fix(web): render one Claude response-viewer message per model message

The Claude reader concatenated every assistant row between two human prompts
into one card, fusing up to 74 distinct model messages into a single card, and
it never read the attachment rows that hold a prompt typed while the agent was
working. Measured over 57 real transcripts on 2026-09-01, the viewer shows
1,806 messages instead of 356 and 353 user cards instead of 178, with the
assistant text sequence unchanged row for row and the response without
?context=full byte-identical on all 57 files.

One assistant row IS one whole model message: in that corpus no assistant row
carries more than one content block and no message id carries more than one
text block, so there was nothing to reassemble. Each row becomes its own
message carrying an additive {kind, label, turn}, and the frontend renders a
same-role run inside one turn as badge-less continuation segments — which is
what keeps a p90 of 11 messages per turn from reading as card spam. A numeric
turn gates that rendering, so Codex, the external-CLI pane parser and an older
server keep one badge per card.

A prompt typed while Claude is working is recorded ONLY as an
attachment/queued_command row. Taking it when origin.kind is 'human' and
commandMode is 'prompt' recovers 162 user cards from 163 such rows — one is a
verbatim repeat inside an unanswered user run and is collapsed by the existing
dedup guard — and restores the turn boundary whose absence let the assistant
runs fuse. The CLI's own queue entries are cleanly separable: of 322
queued_command rows, 159 are commandMode 'task-notification' and not one of
them carries an origin key.

This narrows #169 rather than reverting it: sidechain exclusion, the
restored-<uuid8> rebind, replayed-snapshot dedup and synthetic-row filtering
are all unchanged and still asserted.

docs/architecture-invariants.md

@@ -340,7 +340,7 @@ Anatomy: `.set-shell` → `.set-shell-head` (title + `.set-head-actions`) + `.se
 
 ⚠️ **`Session.lastSubmitAt` is persisted state, not a runtime counter.** `start()` reassigns `_claudeSessionId = resumeSessionId || id` on every launch — including the re-attach path for a mux session that survived the restart — so a recovered pane always points the viewer at its *launch* conversation, even when the CLI moved on via `/clear` hours earlier. The submit anchor is the only thing that can correct that without user input, so it round-trips through `SessionState.lastSubmitAt` and is restored in `restoreMuxSessions()`. Drop it from `toState()` and recovered panes silently show the pre-`/clear` transcript until the user types again. Restoring a *stale* anchor is safe: the resolver's staleness guard rejects any candidate transcript older than the one the pane is currently on, which is exactly the shape of a respawn into a fresh conversation.
 
-⚠️ **Claude transcripts are grouped at real human-turn boundaries, not per JSONL row.** A Claude transcript is an append-only event log, so one logical exchange spans many rows: tool-result rows, meta/image/skill rows, compact summaries, task/team notifications, sidechains, replayed assistant snapshots, and multi-block assistant output. Rendering a card per row was the bug: it produced duplicate and truncated cards that looked like the viewer had lost the response. The grouping walks to the next genuine user turn and dedups replayed assistant snapshots while preserving the tool/task/skill/compact/team metadata filtering. Related: a recovered `restored-<uuid8>` tmux placeholder carries a **stale cwd**, so transcript lookup by working directory finds nothing; it rebinds to the matching top-level Claude transcript UUID instead when that match is unambiguous. Tests: `test/routes/session-routes-claude-last-response.test.ts`. Purely client-side (no `renderIndexHtml` step): the template ships with `btn-response-viewer-header--hidden` and `applyHeaderVisibilitySettings()` (settings-ui.js) toggles it after settings load. Hiding must go through that marker class — the base rule is `display:inline-flex !important`, so an inline style can't override it. `showResponseViewer` is in the `displayKeys` per-device set (settings-ui.js), so it does NOT sync across devices.
+⚠️ **The Claude viewer emits one message per model message and groups them with `turn`; it never concatenates them.** A Claude transcript is an append-only event log, so one logical exchange spans many rows: tool-result rows, meta/image/skill rows, compact summaries, task/team notifications, sidechains, replayed assistant snapshots. Rendering a card per *row* was the original bug (#169) — but the fix overshot to one card per *human turn*, which fused up to 74 distinct model messages into a single card and reported it as one message. One assistant row IS one whole model message: measured across a real `~/.claude/projects` (CLI 2.1.220-2.1.251) no assistant row carries more than one content block and no `message.id` carries more than one text block, so there was never anything to reassemble, and no adjacent pair of assistant rows continues a table, a list, or an open code fence. Each row is therefore its own message carrying `{kind, label, role, text, timestamp, turn}`; the frontend renders a same-role run inside one `turn` as badge-less continuation segments (`.rv-msg-cont`), which is what keeps a p90 of 11 messages per turn from reading as card spam. ⚠️ **A prompt typed while Claude is working is recorded ONLY as an `attachment/queued_command` row** — the CLI never re-emits it as a `user` row — so reading only `user` rows lost 162 of 353 user cards on that corpus AND lost the turn boundary each one carries, which is what let an assistant run fuse in the first place. Take it only when `attachment.origin.kind === 'human'` and `commandMode === 'prompt'`; the CLI's own queue entries (`commandMode: 'task-notification'`) carry no `origin` key at all. The shape is not a documented CLI contract, so every field check must fail closed. ⚠️ **`data.text` (no `?context=full`) is frozen on the last assistant row and must never be derived from `messages.at(-1)`** — agent pollers hash it (`skills/codeman/preamble.sh`), and the last message can be the user's own queued prompt. Replayed assistant snapshots are still deduped, and the tool/task/skill/compact/team metadata filtering is unchanged. Related: a recovered `restored-<uuid8>` tmux placeholder carries a **stale cwd**, so transcript lookup by working directory finds nothing; it rebinds to the matching top-level Claude transcript UUID instead when that match is unambiguous. Tests: `test/routes/session-routes-claude-last-response.test.ts`, `test/response-viewer-turn-segments.test.ts`. Purely client-side (no `renderIndexHtml` step): the template ships with `btn-response-viewer-header--hidden` and `applyHeaderVisibilitySettings()` (settings-ui.js) toggles it after settings load. Hiding must go through that marker class — the base rule is `display:inline-flex !important`, so an inline style can't override it. `showResponseViewer` is in the `displayKeys` per-device set (settings-ui.js), so it does NOT sync across devices.
 **File Viewer button** (header, 1.4.1) is **shown by default on desktop** since `211f3c0` (post-1.8.0): toggle under App Settings → Header & Panels → Header buttons → File Viewer (`showFileViewerButton`, in the per-device `displayKeys` set, fallback default `true`). Purely client-side like the response viewer: the template now ships the button VISIBLE (no `--hidden` class) and `applyHeaderVisibilitySettings()` toggles the `btn-file-viewer--hidden` marker class after settings load; phones still hide it via mobile.css. The button toggles the file-browser panel open/closed without opening the settings modal (`panels-ui.js`). The same commit set the **default desktop header** to WS/CPU/MEM + File Viewer + gear: the token-count chip (`showTokenCount`, no settings-UI toggle) and the lifecycle-log button (`showLifecycleLog`) both default **OFF** now (templates ship them hidden; stored prefs still honored). The plan-usage chip default is unchanged (opt-in, see Plan-usage chip). The **Cron toolbar button** joined the same opt-in pattern in 1.6.0: template ships `btn-cron--hidden`, `applyHeaderVisibilitySettings()` toggles it via the per-device `showCronButton` setting (default OFF, App Settings → Header & Panels → Scheduling); cron jobs themselves are unaffected.
 
 ### Session list layout (header strip vs. left sidebar)