feat(ui): steer a queued follow-up into the live turn after a 5 s edit window (#19970)

## Thinking Path

> - Paperclip is the open source app people use to manage AI agents for
work
> - When a person comments on a task while the agent works, the comment
waits in a queue until the current run ends, and only the next run reads
it
> - Measured locally, a comment posted during a Codex tool call waited
54–68 s for a reply (median 64 s)
> - Codex and Pi can take a message into the live turn ("Steer"), but
today the person must click Steer on each queued message
> - Restart recovery now delivers a steered message that a restart
interrupted (#19962), so steering is safe to do automatically
> - This pull request steers a queued follow-up into the live turn on
its own after a 5-second window in which the person can edit or cancel
it
> - The benefit is a faster reply to mid-turn comments on Codex and Pi,
with no new decision for the person

## Linked Issues or Issue Description

**Feature**
Send a queued follow-up into the running turn automatically when the
runner supports steering.

**Problem**
A follow-up comment posted during a running turn waits for the whole
turn to end and for a new run to start. Steering is available for Codex
and Pi, but only as a manual button on each queued message.

**Proposed behavior**
After a 5-second edit window, the queued message is steered into the
live turn. During the window the row shows "Sending in Xs" with Edit and
Cancel. If steering is unavailable, the message stays queued as before.
Claude, OpenCode and Cursor keep the queue. Steer and Interrupt stay
available as buttons.

Refs #19962

## What Changed

- `queued-message-auto-steer.ts`: one constant,
`QUEUED_MESSAGE_AUTO_STEER_DELAY_MS = 5_000`, a deadline helper and an
eligibility check. A message steers automatically only when all of these
are true:
- steering is available for the queue, and it is a `paperclip_runner_v1`
queue with a queue id and a target run;
  - the person can edit the message;
- it is not an interaction response or a response that requires a fresh
session;
- it is not optimistic, cancelled, already attempted, or open in the
editor.
- `TaskChatQueuedMessages`: countdown row "Sending in Xs" with Edit and
Cancel in place of Steer and the "…" menu. The deadline is `max(message
changed, first eligible) + delay`, so an old queued message does not
send the moment its turn becomes steerable, and an edit restarts the
window. When the deadline passes, the row uses the existing Steer
action, so the server path, idempotency and fallback stay the same.
Cancel returns the row to the normal Steer button. The countdown is
announced once to screen readers, not on every tick.
- `TaskChatThread` turns it on with the constant and passes the message
being edited, so an open edit never sends. The prop stays off by default
for other callers.
- Storybook: `AutoSteerCountdown` (with a play test for Cancel) and
`AutoSteerCountdownMobile` in "Composer / Steering and queued messages".
- Restart chaos TTFT driver: a `midturn` phase measures comment-to-reply
for a comment posted during a 40-second tool call, with `--midturn-mode
queue|steer` and `--midturn-fault K1|K2|K6`. It records the reply count,
so exactly-once delivery is checked.

## Verification

- `pnpm --filter @paperclipai/ui vitest run
src/components/task-chat/TaskChatQueuedMessages.test.tsx
src/components/TaskChatThread.test.tsx`: 434 passed. Seven new
auto-steer tests use fake timers: countdown and send, Cancel, Edit
restarts the window, an open edit never sends, ineligible queues stay
manual, no instant send for an old message, one attempt per revision.
They fail with the trigger disabled.
- `node scripts/check-token-gates.mjs`: clean.
- Storybook in the browser, desktop and mobile: the first row counts
down and steers ("Message steered into the active turn."). The cancelled
row shows the normal Steer button. On mobile the text truncates and the
row fits.
- Mid-turn latency, local, Codex, comment during a 40-second tool call:
queue 54–68 s (median 64 s), steer 47–61 s (median 50 s). The steer was
acknowledged in 0.8–0.9 s. The remaining time is the tool call and the
model, not the hand-off.
- Restart chaos, Codex, steer mode, faults K1, K2 and K6, 2 samples
each, on #19962 plus this branch: 6 of 6 messages acknowledged, still
unread at the fault, recovered, and answered exactly once (before
#19962: 0 of 6).

## Risks

- A message now leaves the queue after 5 seconds unless the person edits
or cancels it. The window and the countdown make this visible, and
steering is only automatic where the provider supports it.
- Pi: a steer the model already read before a restart can arrive again
after recovery, because Pi reports no read evidence (see #19962).
Automatic steering makes this a little more likely.
- If steering fails, the message stays queued and is delivered by the
next run, as today.
- UI only and a test harness. No schema, API or server change.

## Model Used

- Claude Opus 5.5 (`claude-opus-5-5`), Anthropic, via Claude Code with
tool use (shell, file editing, browser checks, test execution).

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have searched GitHub for duplicate or related PRs and linked
them above
- [x] I have either (a) linked existing issues with `Fixes: #` / `Closes
#` / `Refs #` OR (b) described the issue in-PR following the relevant
issue template
- [x] I have not referenced internal/instance-local Paperclip issues or
links (only public GitHub `#NNN` / `github.com/paperclipai/paperclip`
URLs)
- [x] My branch name describes the change (e.g. `docs/...`, `fix/...`)
and contains no internal Paperclip ticket id or instance-derived details
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [ ] All Paperclip CI gates are green
- [ ] Greptile is 5/5 with no open P2s, recommendations, or follow-ups
- [x] I will address all Greptile and reviewer comments before
requesting merge

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

ui/src/components/TaskChatThread.test.tsx

@@ -5036,8 +5036,9 @@ describe("TaskChatThread Paperclip Runner queue", () => {
     let rejectDelivery!: (error: Error) => void;
     const delivery = new Promise<void>((_, reject) => { rejectDelivery = reject; });
     const actionQueue = { ...queue, protocol: action === "interrupt" ? "legacy" as const : queue.protocol };
+    // Exercises the explicit Steer button, so automatic steering is off here.
     const props = { comments: [queuedComment], onAdd: async () => {}, queuedCommentQueue: actionQueue,
-      onSteerQueuedComment: () => delivery, onInterruptQueued: () => delivery };
+      onSteerQueuedComment: () => delivery, onInterruptQueued: () => delivery, queuedMessageAutoSteerDelayMs: null };
     render(<TaskChatThread {...props} />);
     await act(async () => {
       container.querySelector<HTMLButtonElement>(`[data-testid="task-chat-queued-${action}-queued-prp-1"]`)!.click();