RFAI-11: Ambient channel hardening decision and prototype

[Chris0Jeky]

Context

Week 11 from taskdeck-12-week-roadmap-v4.md.

Parent: #972
Depends on: #982
Reuses: #219 for voice-capture privacy posture if voice is the hardened channel.

At the start of this issue, choose one ambient channel to harden based on dogfood signal from #982: desktop voice or VS Code extension. The unchosen channel remains a working prototype only.

Scope

• Decide between desktop voice and VS Code extension based on Week 10 dogfood evidence.
• If voice is chosen, update/reuse CAP-21: Voice capture and transcription integration (opt-in privacy posture) #219 scope for local-first transcription into RawCapture with explicit consent and provenance.
• If VS Code is chosen, prototype selected-text/file-path/git-remote capture using workspace hash instead of full repository content.
• Ship browser-local PWA voice as a small additional prototype if practical.
• Explicitly reject webkitSpeechRecognition because it streams audio to Google.
• Keep marketplace/store publishing out of scope.

Acceptance Criteria

• Decision note records which channel was hardened and why.
• Chosen channel produces RawCapture -> proposal flow with provenance.
• Unchosen channel works for developer dogfood as prototype only.
• Ambient source writes stay proposal-first and pass invariant Claude/create feature f 01 qr r as j4 s14advm nn qhp2 la #1.
• Data-flow/consent language is present for any audio or IDE-context capture.

Suggested Verification

• Manual dogfood script for chosen channel
• Backend/API tests for provenance/source type
• Frontend/extension tests where harness support exists
• Privacy/consent checklist updates when UI behavior lands