fix: retire cancelled extension UI requests

[tamikomssi]

Summary

• add capability-gated extension_ui_cancelled daemon outbound correlation
• retire the exact active terminal dialog when its daemon request aborts or times out
• preserve fail-closed unknown, duplicate, wrong-session, and legacy response handling
• bump daemon schema revision and document the compatibility boundary

Root cause

When Slack consent won the race, the extension aborted its terminal confirmation. Prime Agent deleted the daemon-side pending request without notifying the interactive client. The stale terminal dialog remained clickable, and its late response failed with Unknown extension UI request.

Verification

• base regression at 97b994c: FAIL; one stale response call and one unknown-request UI error
• fixed regression: PASS; exact ID retired and no late response/error
• valid-response negative test: PASS; zero cancellation events
• six touched suites: 508 passed
• npm run check: PASS (Biome 913 files, typecheck, installer render, browser smoke)
• independent Claude Opus 5 security review: PASS, no blocking findings

Real isolated daemon canary

• c299890: FAIL; session-worker cancellation was dropped by the supervisor, and /timed-signal still ended in Unknown extension UI request
• 62659fe: PASS on a fresh run-scoped source daemon/socket/session store; the capable client observed the exact confirmation request and cancellation, the TUI dismissed the dialog, a late Enter produced no response/error, a legacy client received no cancellation, and an actually unknown response remained rejected

Broader-suite note

A full coding-agent run retains unrelated local environment/fixture failures. Every changed suite passes. No production runtime was restarted or deployed.

Upstream contribution gate

Upstream CONTRIBUTING.md requires prior discussion approval. Bug report and invitation request: PrimeIntellect-ai#1964

Rollout gate

This draft is source-only. Installing/restarting the active Prime Agent runtime is separate and requires explicit approval after upstream disposition or an owner-approved local canary.