[silverstein]

Putting AirPods away during a dual-source recording can stop the microphone while system audio continues, leaving the session apparently healthy and most in-room speech missing. This reconnects an available microphone and saves warnings describing the interruption and missing interval.

• Track successful microphone writes independently of system audio and speech amplitude.
• Observe disconnections for default inputs too. Prefer an available configured/default input with a built-in fallback.
• Reuse segmented capture recovery and its existing Stop, stem-preservation, and elapsed-time contracts. Require actual microphone writes before confirming microphone recovery.
• Warn about a stalled source without discarding the surviving input. Retain source warnings in the saved meeting.

Live configuration changes finalized SCRecordingOutput in a signed native test, so recovery creates a new segment instead of editing the active recording's configuration.

Validation at baafe90:

• 482 desktop tests passed; 2,040 core tests passed, one ignored; workspace Clippy with warnings denied and formatting passed.
• Capture-free Swift checks cover fallback selection, silence, retries, PCM, lifecycle, and gap preservation.
• Signed installed Minutes Dev: two injected microphone-only stalls recovered in 3.413s and 3.518s, with both stems and consolidated media saved and gap warnings retained.
• Stop during microphone recovery completed in 1.053s with no surviving capture helper.

The native tests used fault injection on real capture. A physical AirPods removal test is still pending. No production application replacement or release is included.

Fixes #1209.