Queue path parity gaps vs upstream's onSend

[radroid]

Found during the 2026-08-14 sync seam review; both pre-existing, neither caught by typecheck or tests. handleQueueComposerSubmission in ChatView.tsx returns before upstream's onSend handling of:

1. parseStandaloneComposerSlashCommand — with legacy plan mode enabled, typing /plan or /default while in queue mode enqueues the literal text as a message instead of switching interaction mode.
2. expiredTerminalContextCount — upstream toasts when terminal contexts expired between capture and send; the queue path drops them silently (it destructures only sendableTerminalContexts / hasSendableContent from deriveComposerSendState).

Also from the same review, cosmetic decision: queueButton in ComposerPrimaryActions.tsx has no stageBackdropVariant branch, so in artwork identification mode the composer loses the stage treatment whenever Queue is the primary action. Not a revert (Queue is fork-only), just an inconsistency to resolve deliberately.

The enqueue-failure channel half of this review was already fixed in the sync landing (fix(web): surface enqueue failures as a toast, not the maskable error banner).

[radroid]

Plan — 2026-09-12 (blocked on the 09-12 sync landing)

ChatView.tsx is in the conflict set of the in-flight sync #135, and handleQueueComposerSubmission (now at ~:5662) sits a few hundred lines above the onSend path it must mirror (parseStandaloneComposerSlashCommand at ~:6068, expiredTerminalContextCount toast at ~:6078 and ~:6313). Both anchors verified on main @ e39f8be6d; the gap is exactly as described. Sequenced after #135 so the fix is written against the merged file once.

Fix shape (one PR, fork logic hoisted):

1. Hoist the two pieces of onSend pre-processing the queue path lacks into a fork-owned helper apps/web/src/coil/queue/composerSubmitPrelude.ts — resolveStandaloneSlashCommand(trimmed) → { kind: "switch-mode", mode } | { kind: "message" } and expiredTerminalContextsToast(count). Pure, unit-tested.
2. Call it from handleQueueComposerSubmission before enqueue: a /plan / /default in queue mode switches interaction mode instead of enqueuing the literal; expired terminal contexts raise the same toast onSend raises. Upstream's onSend is not refactored to use the helper (that would displace lines); the queue path just gains parity. Net ledger effect on the existing ChatView.tsx row: ~+6/-0.
3. Cosmetic decision: queueButton in ComposerPrimaryActions.tsx has no stageBackdropVariant branch (:135 vs the send branch at :273/:301). Recommend giving Queue the same stage treatment as Send so artwork-identification mode doesn't lose the stage whenever Queue is primary — ~+10/-0 on an existing row. Say if you'd rather leave it.

Tests: helper unit tests only (apps/web has no interaction-test harness). Manual check in test-t3-app after merge: queue mode + /plan switches mode; queue with an expired terminal context toasts.