Fix meeting capture overflow and show recording status in tray

[rteoo]

Small WASAPI packets exhausted the capture event queue during brief consumer or disk stalls, ending meeting recordings with partial audio. Batch contiguous packets and allow bounded backpressure so capture can recover from temporary stalls while preserving append-only storage and visible errors for sustained overload.

The existing non-activating dictation overlay now shows recording time, pause, saving, and partial/interrupted states while the main window is minimized or closed to the tray. Restoring the main window hides it.

Changes also preserve short packet tails at pause/stop and identify native transport overflow in the terminal error. The initial packet establishes the stream clock; later device discontinuities remain visible.

Validation:

• Windows desktop suite: 1,187 tests, 10 skips; 40 focused tests passed, plus a real Tk minimize/restore and focus-preservation smoke.
• MSVC helper build and native self-test passed; Ruff 0.16.3 and diff formatting checks passed.
• A 12-minute microphone/system capture soak with a five-second consumer stall and pause/resume completed without transport overflow or source failure. All 14,369 emitted blocks survived durable readback. Only synthetic silence was persisted, and the temporary fixture was removed.
• Manual privacy review covered the outgoing files, diff, and commit metadata. No secret scanner was available.

Limits: buffering remains bounded, and prolonged stalls can still stop capture with partial audio preserved. The soak retained 15 native discontinuity warnings, so continued capture does not establish loss-free device audio. Packaged startup, MP3 integration (PyAV unavailable), and physical macOS capture remain unverified. The installed app has not been updated.