Answer the user's own inbound FaceTime Audio call

[atomantic]

Summary

• Adds facetime.autoAnswer (default off). With it on and a call-host tab attached, callSession.js's new incoming watcher answers a call from the user's own configured identity and runs it through the existing voice pipeline (whisper STT → voice LLM/persona → Kokoro/Piper TTS), exactly like an outbound call.
• Fail-closed at the helper boundary: facetimeBridge.answer() reports nothing distinguishing "no call" from "an unauthorized caller," so this module never learns an unauthorized caller exists and never logs one — a call from any other handle is simply left ringing.
• Reading the helper (probe) each tick is safe and runs while the watcher is armed; the press (answer) is additionally gated on the call-host tab being attached at press time — answering a call nobody can hear is worse than missing it.
• An authorized call that rings with no host attached, or one the helper fails to press, raises a medium agent_warning notification (deduped once per ring, not once per 2-second tick) instead of silently dropping it.
• Quiet hours only soften the greeting's wording; they never decide whether to answer.
• When the Persistent Mind is running at answer time, the call carries its persona/context and the transcript is handed back to it as a message on hangup, mirroring how an outbound mind-placed call already works; when it isn't running, the call runs the plain voice persona like the widget.
• New voice:call:hangup socket event, routed through endCall() (not a raw facetimeBridge.hangup()) so the session's journal write and mind handoff run the same as any other end-of-call — usable from any tab, not just the call host.
• voice:call:state now also broadcasts to every connected tab via a new callStateEvents emitter (the call-host socket still gets its own direct emit, which drives opening-line delivery). The Mind tab shows an active-call chip with a Hang up button driven by this broadcast.
• Settings → Voice → FaceTime Audio gets an Automatically answer incoming calls toggle with the plain-language rule.

Test plan

• cd server && npx vitest run services/voice/callSession.test.js services/voice/facetimeBridge.test.js sockets/voice.test.js routes/voice.test.js services/persistentMindCallCapability.test.js — watcher tests use an injected probe/answer stub and fake timers (armed-only-while-attached, dedup, mind handoff, quiet-hours greeting, no-log-on-unauthorized).
• cd client && npx vitest run src/components/cos/tabs/MindTab.test.jsx — active-call chip appears from a broadcast even when this tab isn't the call host, and hang up emits voice:call:hangup.
• Full suites green: server && npx vitest run (35549 passed), client && npx vitest run (10262 passed), npm run lint, npm run build.
• Regenerated server/lib/apiRouteCatalog.generated.json and server/lib/socketEventCatalog.generated.json.

Closes #5310
Part of #5306