bug(dictation): join pending operations before committed quit finishes #942

Expected behavior

Committed dictation cleanup closes admission and joins already-admitted work before the history write tail is captured. Pending key/configuration lookups cannot install new streams or a hotkey after cleanup. Existing previews are cancelled through their provider owner.

Confirmed source and regression

At application base 115e26fc9c67316a3b0b1b4318f47f7a2bea3606, cleanup only unregisters the hotkey and clears activeSessions. A stream-stop handler removes its entry before awaiting batch transcription; it can enqueue history after that cleanup returns. A key lookup or hotkey configuration can also complete after the map/hotkey were cleared and publish a new resource.

Source.

Discovered during #919's composition audit. Implemented in branch fix/quit-service-lifecycle, commit e9b88bf5: committed admission, tracked start/stop/hotkey operations and preview-stop promises, late-publication checks, cancellation of active previews, and an awaited producer drain before history settlement.

Three real-IPC-handler regressions cover delayed key resolution, pending batch/history plus independent preview-stop completion, and a late hotkey configuration. They passed in the focused unit lane with provider/native/filesystem boundaries mocked. No live microphone/provider session was used.

Acceptance is producer ordering and ownership. History write failures still belong to their original receipts; this does not promise fsync, failed-write recovery, or native socket-exit evidence beyond the provider API. The forthcoming quit-safety PR may close this specific issue; broader B02/#919 remains open.

Refs #919 and #918.