Restore queued-message visibility above the composer

[iamnbutler]

Summary

Restore the missing message-queue UI so an accepted message no longer appears to vanish while the chat is busy. Related to #24; this is the visibility slice, leaving edit/delete/explicit steering controls open there.

• Project pi’s existing inbox into opt-in chat watch events, including an initial snapshot and committed changes. Include human passive writes, exclude internal writes, and release the queue watch with the transcript watch.
• Show a bounded, scrollable queue above the composer with count, author, invocation mode, full text, and image previews.
• Rebuild from pi on reconnect and remove messages when consumed or withdrawn. No new durable store, data migration, or admission/steering behavior changes. Older clients receive no queue events unless they opt in; new clients still work with older hosts.

Verification

• bun types, bun run ci, git diff --check passed.
• Real source workers with OpenAI gpt-6-astra and existing credentials: live queue updates, passive Chat messages, reconnect snapshot, chat isolation, transfer into transcript, Stop withdrawal, legacy watch opt-out.
• Built and inspected signed Ace-dev using native desktop tools at 1100×760 and 640×600, with two genuinely queued messages and an image preview. Text wrapped and the bounded queue kept the composer available.
• Independent Ace subagent review found no concrete issues.

Built in Ace

Entirely built in Ace: lane, editing, shell builds/checks, CLI protocol smoke checks, subagent review, and native desktop inspection. The native composer AX value write could not be verified; a fresh observation showed no edit, so visual fixtures were submitted through Ace CLI instead (updated #106). Filed #192 for the unrelated existing gpt-4.1-mini tool-schema rejection encountered during validation. Both are linked from dogfooding #5.

[iamnbutler]

Final native check also confirmed that both queued messages (including the image) left the queue and appeared in the transcript after the real sleep tool completed; the queue panel disappeared and the agent acknowledged both. Quit the isolated source Ace-dev run after verification.