docs: Add session debrief about test fixes and MCP tool lesson

add_debug3.py

@@ -0,0 +1,24 @@
+with open("src/app_controller.py", "r", encoding="utf-8", newline="") as f:
+    content = f.read()
+
+# Add debug to show_track_proposal handling
+old = """elif action == "show_track_proposal":
+     self.proposed_tracks = task.get("payload", [])
+     self._show_track_proposal_modal = True"""
+
+new = """elif action == "show_track_proposal":
+     payload = task.get("payload", [])
+     sys.stderr.write(f"[DEBUG] show_track_proposal: task={task}, payload={payload}\\n")
+     sys.stderr.flush()
+     if isinstance(payload, list):
+         self.proposed_tracks = payload
+     else:
+         self.proposed_tracks = []
+     self._show_track_proposal_modal = True"""
+
+content = content.replace(old, new)
+
+with open("src/app_controller.py", "w", encoding="utf-8", newline="") as f:
+    f.write(content)
+
+print("Added debug to show_track_proposal")