feat(uploads): write prompt uploads to a hidden, self-ignoring .codeman-uploads/ folder

A pasted image landed in <workspace>/.claude-images/, a name that belongs to another tool, in a folder nothing ignored, so it showed up in git status of every case that ever received a paste. Uploads now go to a flat <workspace>/.codeman-uploads/ that carries a .gitignore of `*` (written once, never over a file already there): in the workspace because that is the only path identical for a local agent and a container, flat because a nested .codeman/ is the data dir itself when the workspace is the home directory.

The directory names live in paste-image-gc.ts alone. The old folder receives nothing but stays readable for one release: the hourly sweep and the delete cleanup go through uploadDirs(), the image watcher's ignore filter reads the names. uploadDirs() lists only real directories, none that is, contains or sits inside the data dir, and nothing for a remote session, since both consumers delete. The route refuses a remote (SSH) session before touching disk: the file would land on this host under the remote path, where the agent cannot read it.

test/paste-image-dir-shared.test.ts binds port 0 and leaves the port guard's legacy list.

Decided in #553.

docs/api-reference.md

@@ -466,6 +466,21 @@ geometry was read. The capture runs synchronous tmux calls on the server; the
 | `tail=<bytes>` | Keep the newest `<bytes>` of the result (`truncationReason: 'tail'` when it cut). |
 | `lines=<n>` | With `full=1` only: read at most `<n>` lines of tmux history above the visible frame. An integer of at least 1, clamped to the configured history limit; absent or malformed, the whole limit (100,000 lines by default), as before. `truncated` and `truncationReason` describe byte cuts only, not this bound. Without it a full capture reads all of that history before `tail` cuts it, so a client that keeps a fixed number of lines (the tile grid sends its xterm's scrollback plus its rows) should send it. |
 
+## Prompt uploads (`POST /api/v1/sessions/:id/paste-image`)
+
+A `multipart/form-data` body with one `image` part. The file is written into the
+session's workspace as `<workingDir>/.codeman-uploads/paste-<ms>-<hex>.<ext>`, and
+`data` carries `path` and `filename` for the client to type the path into the
+prompt. The folder is Codeman's own: hidden, created on first use with a
+`.gitignore` containing `*` (written once, never over a file already there), and
+cleaned up the way pasted images always were: `paste-*` files older than 7 days
+go in an hourly sweep, and the folder goes when the last session of that
+workspace is killed. Uploads made before this release sit in `.claude-images/`;
+that folder receives nothing new, and is swept and removed the same way for one
+release. A remote (SSH) session answers 400, since the file would land on the
+Codeman host under a path the remote agent cannot read; Docker sessions are
+fine, their workspace is bind-mounted at the same absolute path.
+
 ## Session lineage (`parentSessionId`)
 
 A create request may name the session that spawned it, which the web UI draws as a

docs/architecture-invariants.md

@@ -254,7 +254,7 @@ Further detail, closing: ⚠️ **Closing has the mirror-image race and one owne
 - **No start, attach or relaunch may be in flight** (`Session.paneLifecycleInFlight`, raised for the whole of `_setupOrAttachMuxSession()` and `restartCli()`). The dead-pane respawn revives an exited pane on purpose, and the pane reads as dead until `clearPaneExitForNewPane()` runs after its startup delay.
 - **The pane must have been up for `CLEAN_EXIT_MIN_PANE_LIFETIME_MS` (10 s)** since the last start, attach or relaunch finished (`Session.paneStartedAt`). A CLI that prints a startup error and exits 0 would otherwise lose its tab, and the error with it, seconds after launch; its row stays as `exited (0)` instead. An attach to an already running pane stamps it too, so an `/exit` within seconds of a server restart leaves a row to close by hand.
 
-Scoping needs no check of its own here: `setPaneExit()` already forces `paneExit` to UNKNOWN for direct-PTY, remote, docker and discovered sessions. There is no setting, by the maintainer's decision on #446. ⚠️ Do not flip local panes to `remain-on-exit failed` to get the same effect: a destroyed pane ends the tmux session, the PTY exit nulls the pid, and the browser's `selectSession()` then launches a fresh CLI. `cleanupSession()` keeps `{workingDir}/.claude-images` while another session still uses that directory (`pasteImageDirInUseByOtherSession()`, `paste-image-gc.ts`), since the sweep would otherwise routinely delete a live sibling's pasted images. Paths are compared by `realpath`, and a detached session counts through its persisted record, because `killMux=false` removes it from the map while its pane keeps running; only a session being KILLED is exempt. Each exit gets ONE close attempt (keyed by session id and `at`), and a session being closed refuses `startInteractive()`/`startShell()` (`Session.markClosing()`), so a start that races the close cannot orphan a tmux session. `planRebootRestore()` refuses a record whose persisted `paneExit` is clean (`agent-exited`), which covers an agent that exited just before the power went, before the sweep reached it. Tests: `test/pane-exit-sweep.test.ts`, `test/paste-image-dir-shared.test.ts`, `test/reboot-restore.test.ts`, `test/tmux-manager.test.ts`.
+Scoping needs no check of its own here: `setPaneExit()` already forces `paneExit` to UNKNOWN for direct-PTY, remote, docker and discovered sessions. There is no setting, by the maintainer's decision on #446. ⚠️ Do not flip local panes to `remain-on-exit failed` to get the same effect: a destroyed pane ends the tmux session, the PTY exit nulls the pid, and the browser's `selectSession()` then launches a fresh CLI. `cleanupSession()` keeps `{workingDir}/.codeman-uploads` (and the pre-move `.claude-images`) while another session still uses that directory (`pasteImageDirInUseByOtherSession()`, `paste-image-gc.ts`), since the sweep would otherwise routinely delete a live sibling's pasted images. Paths are compared by `realpath`, and a detached session counts through its persisted record, because `killMux=false` removes it from the map while its pane keeps running; only a session being KILLED is exempt. Each exit gets ONE close attempt (keyed by session id and `at`), and a session being closed refuses `startInteractive()`/`startShell()` (`Session.markClosing()`), so a start that races the close cannot orphan a tmux session. `planRebootRestore()` refuses a record whose persisted `paneExit` is clean (`agent-exited`), which covers an agent that exited just before the power went, before the sweep reached it. Tests: `test/pane-exit-sweep.test.ts`, `test/paste-image-dir-shared.test.ts`, `test/reboot-restore.test.ts`, `test/tmux-manager.test.ts`.
 
 ### Dead-pane respawn: the resume pin
 
@@ -351,7 +351,7 @@ The escape hatch is the synced `workspaceHooksEnabled` setting (App Settings →
 
 ⚠️ Claude-mode only (others carry their conversation id in their own config object), and remote/docker sessions are never offered (`remote-or-docker`), because both need another host or container to be up.
 
-⚠️ A failed rebuild is undone with `discardPartiallyBuiltSession()`, deliberately NOT `cleanupSession()`: the delete path would count the session's tokens into the lifetime totals, demote a pinned record to `stopped` (which this pass reads as an intentional kill, making the session permanently unrestorable) and recursively remove the WORKSPACE's `.claude-images`.
+⚠️ A failed rebuild is undone with `discardPartiallyBuiltSession()`, deliberately NOT `cleanupSession()`: the delete path would count the session's tokens into the lifetime totals, demote a pinned record to `stopped` (which this pass reads as an intentional kill, making the session permanently unrestorable) and recursively remove the WORKSPACE's upload dirs (`.codeman-uploads`, and the pre-move `.claude-images`).
 
 ⚠️ `os.uptime()` reports the HOST's uptime, which a container shares, and that cuts both ways: after a genuine host reboot a containerized Codeman does see a short uptime and the banner works, but a container-only restart is invisible to it, which is the case where this would help most. Tests: `test/reboot-restore.test.ts`, `test/routes/reboot-restore-routes.test.ts`, `test/routes/reboot-restore-rebuild-failure.test.ts`, `test/discard-partially-built-session.test.ts`.
 
@@ -1063,6 +1063,8 @@ Tests: `test/mobile-prompt-composer.test.ts` (in the CI gate, deliberately not u
 
 Target: 20 sessions, 50 agent windows at 60fps. Limits in `src/config/`: terminal 32MB (see below), text 1MB, messages 1000, max agents 500, max sessions 50, max SSE clients 100. **Terminal history** (`src/config/terminal-history.ts`, COD-80): tmux history-limit 100k lines, PTY buffer 32MB max / 24MB trim (env `CODEMAN_MAX_TERMINAL_BUFFER`/`CODEMAN_TRIM_TERMINAL_TO`; the env-derived trim is clamped ≤75% of max — trim ≥ max would disable `BufferAccumulator` trimming entirely = unbounded memory); browser xterm scrollback stays a separate hardcoded 50k (`DEFAULT_SCROLLBACK` in constants.js — 100k/tab is a mobile-memory hazard). tmux <3.7 allocates history at pane creation, so `createSession()` sets the global default in the same command queue immediately before `new-session`; tmux 3.7+ instead creates the session and targets only that pane, because changing the global option can resize and trim unrelated live panes. A settings change resizes tracked panes only on 3.7+ and otherwise affects future panes; no version can recover lines already evicted. Settings keys `terminalScrollbackLines`/`terminalBufferMaxBytes`/`terminalBufferTrimBytes` are schema-validated but inert (only `tmuxHistoryLimit` is wired); `buffer-limits.ts` re-exports the defaults. Text/message limits are env-overridable too (`CODEMAN_MAX_TEXT_OUTPUT`/`CODEMAN_TRIM_TEXT_TO`/`CODEMAN_MAX_MESSAGES`). **Image upload** (`image-input.js` / `config/buffer-limits.ts`): up to `_maxBatchImages` 20 images/batch (bounded concurrency 3), per-file `MAX_PASTE_IMAGE_BYTES` 50MB (env `CODEMAN_MAX_PASTE_IMAGE_BYTES`); the mobile camera-roll picker auto-downscales to fit before upload. **HEIC paste uploads** (#151): converted server-side to JPEG in a `worker_threads` worker (`web/heic-jpeg-worker.ts`, resourceLimits + 30s timeout) gated by `runWithConversionLimit()`; detection is magic-byte based (covers Android/MIUI HEIFs mislabeled as JPEG); headers declaring > 64MP are rejected 415 BEFORE decode (decompression-bomb guard). Deps: `heic-decode` + `jpeg-js`. Use `LRUMap` for bounded caches, `StaleExpirationMap` for TTL cleanup. Anti-flicker pipeline: `docs/terminal-anti-flicker.md`.
 
+**Prompt uploads live in `<workspace>/.codeman-uploads/`** (`POST /api/sessions/:id/paste-image`; the names live ONLY in `src/web/paste-image-gc.ts`): IN the workspace because that is the only path that resolves identically for a local agent and a container (only the workspace is bind-mounted, at the same absolute path; `~/.codeman` is not); hidden so it stays out of `git status` and the agent's view of the repository; FLAT because a nested `<workspace>/.codeman/` IS the data dir (`join(homedir(), '.codeman')`, `src/config/instance.ts`) when the workspace is the home directory, which nothing refuses; and self-ignoring through a `.gitignore` of `*` written once with `wx`, so a file already there is the user's and stays. The pre-move `.claude-images/` receives nothing but stays readable for one release: `UPLOAD_DIR_NAMES` lists both, the hourly sweep and the delete cleanup in `cleanupSession()` go through `uploadDirs()`, and the image watcher's ignore filter reads the names. ⚠️ `uploadDirs()` returns only REAL directories (lstat at the leaf, so a planted `.codeman-uploads -> /other-case/.codeman-uploads` is never listed: `readdir` follows a link to a directory, and the sweep would otherwise age out the other case's uploads through it), none that is, contains or sits inside `getDataDir()` (contrived, `CODEMAN_INSTANCE=uploads` makes `~/.codeman-uploads` the data dir of a home workspace and `CODEMAN_DATA_DIR` can point inside one, but it is one check next to a recursive delete), and nothing for a remote (SSH) session, whose `workingDir` is the remote path and would otherwise name a same-named LOCAL directory for the sweep and the delete. The check is made when the directories are listed: a same-user process that swaps a listed directory for a link during the sweep's awaits is accepted (Node has no `openat()`, and that actor already writes anywhere this process can). The route refuses a remote (SSH) session with 400 before any disk touch: its `workingDir` is the remote path, so the file would land on THIS host where the agent cannot read it. Tests: `test/paste-image-gc.test.ts`, `test/paste-image-dir-shared.test.ts`, the paste-image block of `test/routes/session-routes.test.ts`.
+
 ### Process-tree walks are bounded
 
 **Process-tree walks are bounded** (`proc-tree.ts`, pure + unit tested): `collectDescendants(pid, byParent)` is the ONE descendant traversal, fed by a single cached `ps -eo pid=,ppid=` snapshot (`refreshProcSnapshot()` in tmux-manager.ts: in-flight-shared, async because `execSync`'s timeout cannot return at all while spawnSync waits on an unkillable child, and ANY error discards the result rather than caching a truncated `ps`, which would make whole subtrees invisible to the kill path).