fix(file-viewer): make previewed video seekable and stop it on close

Two bugs in the File Viewer's media player, both reproduced in a real
browser against an 18MB mp4 before and after the fix.

1. Closing the preview left the video playing. closeFilePreview() only
   dropped the overlay's `visible` class, which is display:none and
   nothing else, so the audio kept going with no visible player to pause.
   Detaching the element is not a fix either: a detached HTMLMediaElement
   plays on until it is garbage collected. _stopFilePreviewMedia() now
   pauses, drops src and load()s every media element (also on re-open,
   where overwriting innerHTML had the same effect), which additionally
   aborts the in-flight download.

2. The scrub bar was inert. file-raw read the whole file and answered
   200 with no Accept-Ranges, so Chrome reported video.seekable as
   [0, 0] and silently reverted `currentTime = x`; Safari refuses to
   start such media at all. Raw bodies are now streamed and range-aware:
   Accept-Ranges: bytes on every response, 206 + Content-Range for a
   Range request, 416 for one past EOF, and a malformed spec ignored
   (200) per RFC 9110. Parsing is pure in src/web/http-range.ts.

Measured on tmp/codeman-crt-v5-66s.mp4 (18MB, 66.6s):
  before  seekable [0, 0]     seek to 56.6s reverted to 3.9s   close: still playing
  after   seekable [0, 66.56] seek to 56.6s landed at 60.2s    close: paused, NETWORK_EMPTY

Range slices are byte-identical to `dd`, the full-file path is
byte-identical to the file, and the SVG octet-stream/attachment
hardening and the 50MB cap are unchanged (the cap is still checked
before the range).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -234,6 +234,8 @@ Codeman is a Claude Code session manager with web interface and autonomous Ralph
 
 **File Viewer edit mode** (issue #212): the file-preview overlay edits workspace text files in place — `GET .../file-content?edit=1` + `PUT /api/sessions/:id/file-content`, policy in `src/config/file-editing.ts`. This is a **third file surface and the only one that WRITES**: read-path confinement (realpath + workspace + ownership) plus sensitive/blocked/`.git` denies and an extension **allowlist**; writes are `wx`-temp + rename (no `O_CREAT` anywhere = edit-in-place is structural); optimistic concurrency via sha256 `baseHash` → 409. ⚠️ `edit=1` never truncates and the client must never save a plain-preview buffer (the 500-line truncation would silently delete the rest). ⚠️ CRLF/UTF-8 guards: EOL re-applied server-side, non-UTF-8 refused via round-trip compare. → [architecture-invariants#file-viewer-edit-mode](docs/architecture-invariants.md#file-viewer-edit-mode), `docs/file-viewer-edit-plan.md`
 
+**Raw file bodies are streamed and range-aware**: `file-raw` and the attachments `/raw` route always advertise `Accept-Ranges: bytes` and answer a `Range` header with `206` + `Content-Range` (single-range only; parser is pure + unit-tested in `src/web/http-range.ts`, a malformed spec is ignored → 200 while an out-of-bounds one is a 416). ⚠️ A 200-only response is what made the File Viewer's `<video>` unseekable: Chrome then reports `video.seekable` as `[0, 0]`, the scrub bar is inert and `currentTime = x` silently reverts (measured on an 18MB mp4), and Safari refuses to start the media at all. ⚠️ These bodies go out through `reply.hijack()`, which bypasses Fastify's status handling — `sendRawStream` must copy the status onto `reply.raw` by hand or a partial body ships labelled `200` and the browser treats a slice as the whole file. ⚠️ Closing the preview must **pause and unload** the media (`_stopFilePreviewMedia` in panels-ui.js): dropping the overlay's `visible` class is `display:none` and nothing else, and a DETACHED `HTMLMediaElement` keeps playing, which is how the X button used to leave a video audible with no player to pause.
+
 **Ultracode / workflow-run visualization** (opt-in, default OFF): the Workflow tool writes a completion artifact only at run *end*, so live in-flight runs exist solely as transcript dirs. `workflow-run-watcher.ts` therefore synthesizes ACTIVE runs from transcripts until the completion artifact appears and supersedes them. It is **STANDALONE** and deliberately never imports or touches `subagent-watcher.ts`, despite reading the same tree. Two independent toggles: `showUltracodeAgents` (docked panel) and `ultracodeFloatingWindows` (floating windows); the watcher starts if **either** is on. → [architecture-invariants#ultracode--workflow-run-visualization](docs/architecture-invariants.md#ultracode-and-workflow-run-visualization)
 
 **Clone a repository as a case** (issue #236, Add Case → **Clone Repo**): `POST /api/cases/clone` clones a public repo into the caller's case space synchronously (request held open, bounded by `GIT_CLONE_TIMEOUT_MS`, no job store); `POST /api/cases/clone-preflight` reports whether the URL can be cloned anonymously plus its real branches/tags. Core in `src/git-clone.ts`. ⚠️ **The URL is a code-execution surface**: `ext::sh -c <cmd>` (and ANY `<name>::<payload>` helper) makes git run a command, so every `::` form is refused, a leading `-` is refused, and every spawn is an argv array with `--` before the operands. ⚠️ **Non-interactive or the open request hangs** — `gitNonInteractiveEnv()` closes the terminal/askpass/ssh/GCM prompt paths; `HOME`/`PATH` stay inherited, so a user's OWN credential helper may authenticate (Codeman still never collects or stores credentials, and refuses a `user:password@` URL). ⚠️ Timeout kills the process GROUP (clone fans out into child processes), the destination is removed only if this attempt created it, and repository contents win over scaffolding (existing `CLAUDE.md` kept, hooks merged, repo-shipped `.claude/settings*` reported as a warning since its hooks run locally). The **Brain** picker sets the toolbar run mode on success. → [architecture-invariants#clone-a-repository-as-a-case](docs/architecture-invariants.md#clone-a-repository-as-a-case)