The hold-to-talk release path called AsyncStream.Continuation.finish()
while holding MacAudioRecorder's NSLock; onTermination re-entered the
same lock on the main thread and froze the app. Finish snapshot sinks
outside the lock and guard the audio tap once stop() begins.
The dictation HUD no longer reassigns its hosting view and forces a
synchronous relayout on every view-model tick; it uses a fixed panel
size and SwiftUI @ObservedObject refresh instead.
Adds OSGKeyboardMacTests with a regression test that fails under the
old lock re-entry pattern.
Rocky