Voice in the chat 1/3: mode control, Text and Talk, speaker control #334

Part of the voice-in-the-chat epic #333 (linked as parent). Waits on the epic's needs-review approval.

Mockup: see #333.

User story

As a person talking to eve by voice, I want my spoken turns and eve's replies shown as chat text, so that I can read answers while I talk.

Acceptance criteria

• The chat screen shows a mode control with three choices: Text, Talk and Hands-free.
• One tap on the mode control changes the mode.
• In Text and Talk modes, the chat shows each spoken turn and each reply as text.
• A spoken turn shows a microphone mark.
• In Talk mode, eve records speech only while the person holds the Talk button.
• In Talk mode, the chat shows the person's words while they speak.
• The speaker control sets whether eve speaks replies in Text and Talk modes.
• The speaker control is off on a device that has not set it.
• The device keeps the speaker setting after a reload.
• In Text and Talk modes, the person can attach an image to their next turn.
• The desktop and the phone show the same mode control.

What I'd notice: a Text · Talk segment above the chat box, a speaker button in the chat header, and a big hold-to-talk button in Talk.

Tasks

• Mode control in the chat composer (Hands-free segment present, wired in batch 2).
• Talk: hold button reusing stt-manager.js; live words in the pending bubble.
• Speaker control in the chat header; device-local, off by default.
• Microphone mark on spoken turns.
• Image attach beside the hold button.
• Carry docs/mockups/ from feat/333-voice-in-chat into main with this PR.
• Feature map rows and a journey for the simple path.

Contract

Pinned by the planner on #333 ("#334: mode control, Text and Talk, speaker"); copied here so the ownership is on this issue.

Ownership:

• 1A (UI): public/voice-modes.js (new), public/index.html, public/apple/voice.css, public/features/tts.js, public/app.js, public/panes/views.js, public/core/constants.js, public/message-renderer.js, CLAUDE.md, docs/mockups/voice-modes.html, docs/mockups/voice-modes.png.
• 1B (partials): public/stt-manager.js, public/stt-server-backend.js, public/message-dispatcher.js, ws/voice-messages.js, docs/api.md.
• Tests: test/e2e/g9-voice-modes.spec.js (new), docs/FEATURES.md (G9.38–G9.42, retire G9.32 and G9.34).

Interfaces, wire shapes and waits: see the contract comment on #333.