fix: qualify speech before barge-in output control

[rogerchappel]

Summary

• hold barge, duck, and cancel events until speech survives max(minSpeechMs, debounceMs)
• restore agent_speaking when a transient candidate falls below threshold
• document the timing contract and cover transient, sustained, and disabled output-control policies

Commits

• a9b7bfb test: define qualified barge-in timing
• bc2591c fix: gate barge-in events on qualified speech
• 82ec60a docs: specify qualified barge-in events

Verification

• npm ci
• npm run release:check (47 tests, typecheck, build, smoke, installed-doc/import/package checks)
• git diff --check origin/main...HEAD

Changed 3 files (+81/-37). All commits are authored and committed by Roger Chappel miscanalysis@gmail.com.

[rogerchappel]

Automated merge note

Triage class: auto-merge

Summary: Gates barge-in, duck, and cancel events on qualified sustained speech; restores agent-speaking state after transient candidates; adds deterministic regression coverage and aligns state-machine documentation.

Checks run: GitHub CI verify completed SUCCESS; worker verification npm ci, npm run release:check (47/47 tests, syntax, typecheck, build, smoke, installed docs/imports/package checks), and git diff --check origin/main...HEAD passed. Final diff (3 files, +81/-37), mergeability, branch protection, author/committer identity, and checks were re-read immediately before merge.

Rebased/CI-repaired: No.

Verified head SHA: 82ec60a0ff5747e221f12d584fbaa7bebabc8869.