feat(composer): long-press send button to queue message

[bjspi]

Linked issue

None yet. There's no prior issue or design discussion for this. Per CONTRIBUTING.md, a new feature normally wants a linked issue + design alignment first — happy to file a feature request and discuss scope/fit before you spend time on this, or to close it if long-press-to-queue isn't a direction you want. Opening as a draft for visibility.

Type of change

• Bug fix
• New feature (interaction/UX change — no prior design alignment yet, see above)
• Refactor / code improvement
• Docs

What does this PR do

Adds a long-press gesture on the send button that queues the current draft instead of sending it. Tap/click still sends exactly as before — behaviour on a normal press is unchanged.

It does not introduce a new queue mechanism. It reuses the existing one (queueComposerMessage / onQueue / the session queuedMessages store) that already powers the sendBehavior: "queue" setting and the Mod+Enter shortcut. This PR just exposes that same path through an additional trigger, so mobile users can queue a follow-up while an agent is running without changing a setting.

Concretely:

• New pure helper runLongPressQueueAction in composer/input/state.ts (queues, then fires an optional side effect only if something was actually queued).
• queueMessageImpl now returns whether it queued, so the native haptic only fires on a real queue.
• The send button gains onLongPress (gated to the normal send state and to composers that actually support queueing) plus an accessibilityHint reusing the existing composer.input.queueMessage string — no new i18n keys.
• Medium haptic feedback on native (expo-haptics, isNative-gated) so the queue action is felt on mobile.

Three files changed: composer/input/input.tsx, composer/input/state.ts, composer/input/state.test.ts.

How did you verify it

Honest disclosure up front: I have not run the app on a device/simulator, so there are no per-platform screenshots or video yet. I don't want to pass off automated checks as UI testing. What I actually ran, locally on this branch:

• npm run test --workspace=@getpaseo/app scoped to packages/app/src/composer → 97 tests pass (12 files), including 3 new unit tests for runLongPressQueueAction (no-op when queueing unavailable; fires the side effect only when a message is queued; skips it when there's nothing to queue).
• npm run typecheck (app workspace, after build:client + build:server deps) → clean.
• npm run lint on the changed files → 0 warnings, 0 errors.
• npm run format (oxfmt) → all three files already match.

What I have not done and what this still needs before merge:

• Real on-device verification of the gesture on iOS, Android, desktop, and web (tap still sends; ~500 ms hold queues + haptic on native; queued item shows in the queue track; auto-dispatches on the running→idle transition). The queue logic itself is the existing, already-shipping path, but the long-press trigger and haptic have only been exercised by unit tests, not by hand on each platform.

Glad to gather that evidence or hand it off — flagging clearly rather than implying testing I didn't do.

Checklist

• One focused change. Unrelated cleanups split out.
• npm run typecheck passes
• npm run lint passes
• npm run format ran (Biome/oxfmt)
• UI changes include screenshots or video for every affected platform — not done yet (see above)
• Tests added or updated where it made sense