feat: detect clamshell mode and skip built-in mic when lid is closed

[pascalwhoop]

Summary

Fixes #566

When a MacBook lid is closed in clamshell mode the built-in microphone stays visible in CoreAudio's device list but is physically inaccessible. The existing kAudioHardwarePropertyDevices listener never fires (nothing actually disconnects), so VoiceInk had no way to know the mic was unusable and kept trying to use it.

• Subscribe to NSApplication.didChangeScreenParametersNotification in AudioDeviceManager to detect display configuration changes
• Call CGDisplayIsBuiltin() on each active screen's display ID — when no built-in display is found, the lid is closed (isClamshellMode = true)
• All three device-selection paths now skip the built-in mic in clamshell mode: findBestAvailableDevice, selectHighestPriorityAvailableDevice, and getCurrentDevice (custom mode)
• If there is truly no alternative mic available the built-in is used as a last resort rather than returning nothing
• State is seeded at launch so the app behaves correctly when started while already docked in clamshell mode
• Active recordings are never interrupted by a lid-close event

Test plan

• Start VoiceInk with laptop open (no external display) — internal mic selected as expected
• Connect external display and close lid — app should automatically switch to next available mic (e.g. AirPods, USB mic) without user interaction
• Open lid again — built-in mic becomes eligible for selection again
• Launch VoiceInk while already in clamshell mode — built-in mic is skipped from the start
• Test all three input modes (System Default, Custom, Prioritized) with lid close/open cycle
• Verify an active recording is not interrupted when the lid is closed mid-session

🤖 Generated with Claude Code

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Summary by cubic

Detects clamshell mode and skips the built-in MacBook mic when the lid is closed, so we auto-select a usable external mic. Fixes #566 and keeps ongoing recordings uninterrupted.

• New Features
  • Detect clamshell mode via display change notifications (NSApplication.didChangeScreenParametersNotification) and CGDisplayIsBuiltin; seed state at launch.
  • Skip the built-in mic in System Default, Prioritized, and Custom modes when the lid is closed.
  • Fall back to the built-in mic only if no other input is available.
  • Never switch devices mid-recording when the lid closes.

^{Written for commit 549b890. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 1 file

[jonnywilliamson]

Yes, I noticed this as well. And the only way around it for me was to use the priority list with the other microphones above the MacBook Pro one.