fix: recover unsupported audio input routes

[jatinkrmalik]

Summary

• let AVAudioEngine bind input taps to the live hardware format so USB, Bluetooth, and virtual route changes cannot leave the tap using a stale format
• convert each callback using the format of the buffer Core Audio actually delivered
• stop and surface a microphone-route error when an engine starts but delivers no buffers for three seconds, preventing Test Dictation from remaining stuck

User report

This addresses the VocaMac 0.8.0 logs from Fraser showing repeated Input HW format and tap format not matching failures on EVO4 and oscillator routes, plus captures that started without receiving microphone audio.

Validation

• swift test --filter AudioEngineTests|AppStateRecordingTests: 45 passed
• swift test: 399 passed, 1 expected Accessibility-dependent skip
• swift build -c release: passed

[jatinkrmalik]

/build

[github-actions]

⏳ PR Build started for 110b1ac

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[github-actions]

✅ PR Build ready!

DMG	VocaMac-0.8.0-pr.234+110b1ac-arm64.dmg
Size	28M
Branch	jmalik/fix-audio-input-route
Commit	110b1ac
Signed	✅ Developer ID
Notarized	✅ Apple

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1. Click the DMG link above to download
2. Open the DMG and drag VocaMac to Applications (replace existing)
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SHA-256 checksum

ff85064c6f8d54ea9a52c55205b43a89bb991b21b7b08af5f32b42fbb71ae9ea  VocaMac-0.8.0-pr.234+110b1ac-arm64.dmg

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[Mr-Sunglasses]

This will be slate and can be close when #233 merged, cause it solves it.

[jatinkrmalik]

Closing in favor of #233