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/VaultTranscriptStore.cs

@@ -49,6 +49,25 @@ public sealed class VaultTranscriptStore : ITranscriptStore
             cancellationToken);
     }
 
+    public Task AppendLinesAsync(
+        TranscriptSession session,
+        IReadOnlyList<string> lines,
+        CancellationToken cancellationToken)
+    {
+        if (lines.Count == 0)
+        {
+            return Task.CompletedTask;
+        }
+
+        return WithFileGateAsync(
+            session.TranscriptPath,
+            () => File.AppendAllTextAsync(
+                session.TranscriptPath,
+                string.Concat(lines.Select(line => line + Environment.NewLine)),
+                cancellationToken),
+            cancellationToken);
+    }
+
     public async Task ReplaceLineAsync(
         TranscriptSession session,
         TranscriptLineReference lineReference,