H-6763: Add the voice interview experience

[kostandinang]

🌟 What is the purpose of this PR?

This PR turns the H-6763 composer microphone into a persistent, half-duplex interview experience. Domain experts can hear canonical Brunch questions, answer by voice, review finalized transcripts, correct an answer, pause or interrupt playback, fall back to typing, and end the interview without losing the surrounding conversation.

It is stacked on #9378 and keeps provider-specific OpenAI transport, transcription, and synthesis in the Petrinaut website host while exposing a provider-neutral interview stage through Petrinaut. The remaining upstream ask-emission contract and credentialed end-to-end witness are called out below rather than hidden behind the UI.

🔗 Related links

• H-6763: Support for realtime audio interviewing of domain experts (internal)
• #9378: Improve voice preview reliability diagnostics — required parent PR
• ADR-0009: OpenAI voice UI turn shell
• Condition-5 turn-latency assessment

🚫 Blocked by

• #9378
• An accepted Brunch/Flue contract that emits the terminal brunch_ask before background sweep/settlement. The controller consumes an emitted ask immediately, but current upstream ordering can still delay emission; the UI deliberately does not claim answer readiness before a canonical ask exists.

🔍 What does this change?

• Adds a provider-neutral interview-stage API to Petrinaut and an OpenAI-backed implementation in @apps/petrinaut-website.
• Keeps one controller and WebRTC session alive across full sidebar, compact sidebar, and detached bottom-bar presentations. Placement changes do not reconnect or reopen the microphone; recoverable errors reopen the full stage.
• Separates interview-answer capacity from generic chat readiness, speaks emitted brunch_ask text before settlement completes, and records finalized-answer → question-visible/spoken/answer-ready latency.
• Implements explicit half-duplex turn taking: playback completes before capture opens, Interrupt and speak cancels playback first, and Done speaking closes capture while provider VAD remains the single commit authority.
• Adds a real RMS microphone meter whose audio context is resumed from the start action, plus reduced-motion and text equivalents.
• Distinguishes provisional and committed transcripts, gates redo/edit controls on actual correction capacity, preserves rejected correction drafts, and clears prior-answer state when an interview ends.
• Keeps the current question and keyboard composer visible, protects active interviews from Clear Chat, and presents authoritative covered/still-exploring topics without speculative projection or question counts.
• Adds disclosure and consent, accessible responsive controls, Petrinaut user documentation, and the required Petrinaut changeset.

Pre-Merge Checklist 🚀

🚢 Has this modified a publishable library?

This PR:

• modifies an npm-publishable library and I have added a changeset file(s)

📜 Does this require a change to the docs?

The changes in this PR:

• require changes to docs which are made as part of this PR

🕸️ Does this require a change to the Turbo Graph?

The changes in this PR:

• do not affect the execution graph

⚠️ Known issues

• The accepted upstream ask-before-settlement contract described in Blocked by is not yet available, so upstream work can still delay when the next question is emitted.
• The authoritative projection contract is not available. This PR therefore leaves Petrinaut's main canvas as the model surface instead of rendering a speculative preview.
• No credentialed OpenAI + Brunch browser witness was available. Browser review covered start, responsive layout, microphone-error recovery, keyboard fallback, Clear Chat protection, and accessibility, but not real synthesis quality or end-to-end turn latency.

🐾 Next steps

• Establish terminal-ask emission before background settlement and capture the requested answer-to-next-question latency witness.
• Run a credentialed expert witness covering interruption, vocabulary rendering, microphone feedback, correction flows, and presentation transitions.
• Connect the emerging model to Petrinaut's main canvas when the authoritative projection contract is available.

🛡 What tests cover this?

• yarn workspace @apps/petrinaut-website test:unit — 18 files and 130 tests covering the realtime session, turn controller, speech playback, responsive interview controls, diagnostics, and mocked integration boundary.
• yarn workspace @hashintel/petrinaut test:unit — 28 files and 220 tests covering the host API, conversation lifecycle, answer queue, Clear Chat protection, and panel integration.
• Brunch transport and app unit suites cover interview-answer routing and terminal ask behavior.
• Website and Petrinaut TypeScript/ESLint checks cover the affected packages; formatting and Markdown lint pass for the changed files and user guide.
• Browser checks cover desktop and 390 px layouts, recovery behavior, and the affected sidebar's WCAG A/AA axe audit.

❓ How to test this?

1. Configure the Petrinaut website with the OpenAI voice preview enabled, a valid OpenAI API key, and a Brunch chat endpoint.
2. Open the AI sidebar and select Start voice interview. Confirm disclosure and consent appear before microphone access, then start the interview.
3. Confirm the canonical question is visible and spoken before the microphone opens, and that the microphone meter responds only while capture is active.
4. Exercise Done speaking, pause/resume, minimize/expand, sidebar close/reopen, Interrupt and speak, redo, typed correction, and keyboard fallback. Confirm presentation changes alone do not reconnect or change microphone state.
5. While an interview is active, confirm Clear Chat is disabled. Trigger a recoverable microphone or network error and confirm the sidebar reopens to the full recovery stage.
6. Confirm correction controls remain disabled while an answer is being written down, rejected correction text remains editable, and ending/restarting does not expose the prior answer.
7. At a 390 px viewport, confirm the full stage stays above the composer and the detached compact presentation becomes a bottom bar.

📹 Demo

https://www.loom.com/share/4592af568cf144cd9f58c0b579da6492

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[CLAassistant]

All committers have signed the CLA.

[semgrep-code-hashintel]

Semgrep found 1 regex_dos finding:

• apps/petrinaut-website/src/voice-diagnostics.ts
  • L139-146 - Triage

Ensure that the regex used to compare with user supplied input is safe from regular expression denial of service.

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