Preserve recovery transcripts and add user-approved agent requests

Append successful offline recovery with a duplicate-warning marker and retain failed replay sources. Offer newly available microphones through confirmation notifications.

Add project discovery metadata and blocking association approval, plus nonblocking workflow requests that start a separate settings-agent conversation. Include regression tests, OpenSpec changes, and verified local Release startup.

MeetingAssistant/Recording/IMicrophoneSwitchPromptService.cs

@@ -0,0 +1,12 @@
+namespace MeetingAssistant.Recording;
+
+public interface IMicrophoneSwitchPromptService
+{
+    Task<bool> ConfirmSwitchAsync(MicrophoneDevice microphone, CancellationToken cancellationToken);
+}
+
+public sealed class NoopMicrophoneSwitchPromptService : IMicrophoneSwitchPromptService
+{
+    public Task<bool> ConfirmSwitchAsync(MicrophoneDevice microphone, CancellationToken cancellationToken)
+        => Task.FromResult(false);
+}