feat: add transcription pause controls

docs/meeting-assistant-configuration.md

@@ -38,6 +38,7 @@ This example is abbreviated so the most common shape is readable. The checked-in
         "FirstPromptAfter": "00:02:00",
         "ReminderPromptAfter": [ "00:05:00", "00:10:00" ],
         "AutoStopAfter": "00:30:00",
+        "MaximumPauseDuration": "04:00:00",
         "InferredEndPadding": "00:01:00",
         "CheckInterval": "00:00:15"
       }
@@ -131,20 +132,23 @@ The default profile is always named `default`. Non-default profile hotkeys are r
 
 During recording, Meeting Assistant captures microphone and system loopback separately, buffers both streams to align samples, cleans the microphone stream through a local adaptive echo canceller using loopback as the far-end reference, then mixes the cleaned microphone and system streams into the normal 16 kHz mono PCM chunks. If one source is quiet beyond the alignment timeout, the available source is mixed with synthetic silence so microphone-only speech and system-only playback keep flowing to transcription.
 
+The tray's fine-grained controls expose `Pause transcription` while a meeting is active and `Unpause transcription` while it is paused. Pause does not stop audio devices, finish the meeting, replace the speech-recognition pipeline, or reset run-local speaker mappings and collected samples. Instead, each captured mixed chunk is replaced with equal-length PCM silence before it reaches the temporary WAV, live speaker buffer, or configured transcription provider. This discards real audio from the paused interval while preserving the provider session and meeting-relative timing. In particular, Azure keeps the same active `ConversationTranscriber` and push stream; pause therefore does not suspend Azure connection time or billing. `Finish meeting` and cancel/discard remain available while paused, and `/recording/status` reports the state in `isPaused`.
+
 On Windows, `Recording:MicrophoneDeviceId` can pin capture to a specific active microphone endpoint id. Leave it blank to follow the Windows default capture endpoint. The tray icon menu also exposes `Microphone`, listing active microphone endpoints with the effective endpoint checked. Selecting a microphone there overrides the configured/default microphone for later recording starts until another microphone is selected or the process exits.
 
 `Recording:MicrophoneMixGain` and `Recording:SystemAudioMixGain` are applied during the final mix and default to `1`. `Recording:TemporaryRecordingsFolder` controls where the temporary mixed WAV is written while the run is active. Temporary WAV files are deleted after the run completes, and stale temporary recordings from interrupted runs are deleted when the application starts. If an Azure Speech meeting cannot drain transcription before `Recording:StopProcessingTimeout`, Meeting Assistant keeps the WAV and writes a durable backlog item under `TemporaryRecordingsFolder\offline-transcription-backlog`. The background backlog worker retries those queued meetings, replays each WAV through a fresh speech pipeline, rewrites the original transcript, completes meeting metadata and summary generation, then removes the backlog item and WAV.
 
 `Recording:MaxMetadataAttendeeImportCount` limits how many attendees Outlook metadata enrichment imports into meeting-note frontmatter. The default is `30`; when an appointment has more attendees than that, Meeting Assistant still imports title, agenda, and scheduled end time, but leaves attendees empty because large invites are usually presentation-style meetings.
 
-`Recording:InactivitySafeguard` watches active recordings for long periods without transcript text. The timer starts at meeting start and resets whenever a live transcript segment with text arrives. By default the app asks whether to stop after 2, 5, and 10 minutes of inactivity through native Windows app notifications with action buttons, requests reminder-style toast behavior, keeps each stop reminder actionable for 1 minute, and automatically stops normally after 30 minutes. Ignoring a notification does not block later checks or auto-stop. Safeguard stops are not aborts: transcription drain, speaker processing, screenshots, and summary generation continue through the normal stop flow. When the safeguard stops a run, the meeting end time is inferred as the last transcript segment timestamp plus `InferredEndPadding`; if no transcript text arrived, it uses meeting start plus the same padding.
+`Recording:InactivitySafeguard` watches active recordings for long periods without transcript text. The timer starts at meeting start and resets whenever a live transcript segment with text is written. Writing new transcript text also dismisses every outstanding inactivity notification and invalidates its actions. By default the app asks whether to stop after 2, 5, and 10 minutes of inactivity through native Windows app notifications with Yes, No, and `Pause transcription` actions, requests reminder-style toast behavior, keeps each stop reminder actionable for 1 minute, and automatically stops normally after 30 minutes. While transcription is intentionally paused, those prompts and the ordinary transcript-inactivity stop are fully suspended. A separate `MaximumPauseDuration`, defaulting to 4 hours, normally stops a meeting that remains continuously paused without showing an inactivity notification; it remains active when the ordinary inactivity safeguard is disabled, while a non-positive value disables the paused-session cutoff. Unpausing clears the continuous-pause timer and restarts transcript-inactivity timing from that moment. Ignoring a notification does not block later checks or auto-stop. Safeguard stops are not aborts: transcription drain, speaker processing, screenshots, and summary generation continue through the normal stop flow. When transcript inactivity stops a run, the meeting end time is inferred as the last transcript segment timestamp plus `InferredEndPadding`; if no transcript text arrived, it uses meeting start plus the same padding.
 
 | Setting | Purpose |
 | --- | --- |
-| `Enabled` | Enables the inactivity safeguard for active recordings. |
+| `Enabled` | Enables transcript-inactivity prompts and `AutoStopAfter`; `MaximumPauseDuration` remains independent. |
 | `FirstPromptAfter` | First transcript-inactivity duration before showing the stop prompt. |
 | `ReminderPromptAfter` | Additional transcript-inactivity durations before showing another stop prompt. |
 | `AutoStopAfter` | Transcript-inactivity duration after which Meeting Assistant stops the recording normally without prompting again. |
+| `MaximumPauseDuration` | Maximum continuous transcription pause before Meeting Assistant stops the meeting normally without an inactivity notification; defaults to 4 hours, and a non-positive value disables it. |
 | `InferredEndPadding` | Padding added to the last transcript timestamp, or meeting start when no transcript arrived, for safeguard-triggered end times. |
 | `CheckInterval` | Polling interval for checking the active recording inactivity state. |