Fix mic access errors

[lukechatton]

Summary

• prevent voice mic startup from crashing when the selected mic device cannot be resolved
• add defensive null/readiness checks before starting UniVoice recording
• remove duplicate mic-start trigger in main-menu microphone toggle flow

Problem

Users could hit a System.NullReferenceException in Bridge.StartMicRecording when currentDevice was null/stale (for example after device list/name mismatches like Audio Out).
The mic toggle path in settings also triggered recording twice, causing duplicate start attempts/log spam.

Root Cause

• SetMicDeviceIndex relied on direct name matching against UniMic devices; when no match was found, currentDevice remained null.
• StartMicRecording assumed currentDevice was valid.
• UI toggle path called both PickMicAndStartRecording() and SetMicrophoneEnabled(true) (which already calls PickMicAndStartRecording()).

Changes

airship

• Bridge.cs
  • harden mic resolution in SetMicDeviceIndex:
    • exact match, then case-insensitive match
    • fallback to first valid available mic
  • harden StartMicRecording:
    • recover if currentDevice is null/stale
    • log warning and return if no valid mic exists
  • add helper methods:
    • ResolveMicDeviceByName
    • ResolveFirstMicDevice
• AirshipUniVoice.cs
  • add guard clauses in StartRecording(Mic.Device mic):
    • return with error log if mic == null
    • return with error log if ClientSession == null

airship-testbed (#718)

• MicrophoneSettingsPage.ts
  • remove redundant clientSettings.PickMicAndStartRecording() call from voice-toggle handler
  • rely on clientSettings.SetMicrophoneEnabled(true) to perform single start path

Behavior After

• no exception when selected mic cannot be resolved; code now falls back safely or exits with warning
• mic toggle performs one start attempt instead of two
• clearer logs for invalid device/session states

Assumptions

• fallbacking to first valid input device is preferable to failing hard
• if no valid microphone device is present, recording should not start and should fail gracefully

Impacted Repos

• airship
• airship-testbed