Prevent audio-device changes from stalling dictation hotkeys

[supfeer]

Description

Prevents audio-device topology changes from leaving dictation permanently unresponsive.

An AVAudioEngine can block during deallocation in Apple's hardware-format path. Retirement previously used a serial queue without a deadline, so later hotkey callbacks reached ASRService.start() but waited forever for the poisoned queue.

This PR:

• bounds audio-engine retirement and barrier waits with a three-second watchdog
• propagates retirement timeouts through compatibility startup and route recovery so start/stop state remains retryable
• attempts direct Core Audio capture before waiting on an old AVAudioEngine retirement

Type of Change

• 🐞 Bug fix
• ✨ New feature
• 💥 Breaking change
• 🧹 Chore
• 📝 Documentation update

Related Issue or Discussion

Closes #682.

Testing

• Tested on Intel Mac
• Tested on Apple Silicon Mac
• Tested on macOS version: 26.5.2
• Ran linter locally: swiftlint --strict --config .swiftlint.yml Sources
• Ran formatter locally: swiftformat --config .swiftformat Sources
• Ran tests locally: xcodebuild test -project Fluid.xcodeproj -scheme Fluid -configuration Debug -destination 'platform=macOS' -derivedDataPath DerivedData DEVELOPMENT_TEAM=2GT974SA8P -only-testing:FluidDictationIntegrationTests/AudioEngineRetirementDrainTests -quiet

Additional checks:

• swiftlint --strict --config .swiftlint.yml Sources passed with 0 violations in 136 files.
• swiftformat --lint --config .swiftformat Sources was run without modifying files, but the repository-wide baseline failed because 60 of 136 existing files require formatting; no formatting changes are included in this focused bug-fix PR.
• ./build.sh completed successfully with a signed Debug build.
• git diff --cached --check passed before commit.
• Field log inspection confirmed hotkey callbacks continued firing while retirement barriers timed out after a real soundcore Liberty 5 Pro route change.

Screenshots / Video

• No UI/visual changes; screenshots/video are not applicable.

Notes

• Direct Core Audio remains controlled by the existing Faster Recording Start setting; this PR does not change its default or persisted value.
• AudioEngineRetirementDrainTests covers off-main release ordering and bounded timeout recovery.
• Physical Bluetooth connect/disconnect remains a manual hardware regression scenario; the unit test does not claim to emulate a Bluetooth route.

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