fix(ui): stream phase progress without gates

backend/test/session-bridge.test.ts

@@ -42,6 +42,29 @@ test("real Pi thinking_delta becomes a dedicated activity_delta to the FE", () =
   expect(seen).toEqual([{ type: "activity_delta", text: "Valuto le ambiguità" }]);
 });
 
+test("a reserved phase notification becomes a structured phase_started event", () => {
+  const { rpc, fire } = fakeRpc();
+  const bridge = new SessionBridge(rpc);
+  const seen: any[] = [];
+  bridge.onClientEvent((event) => seen.push(event));
+
+  fire({
+    type: "extension_ui_request",
+    method: "notify",
+    notifyType: "info",
+    message: "__tht_phase_started__:F2",
+  });
+  fire({
+    type: "extension_ui_request",
+    method: "notify",
+    notifyType: "info",
+    message: "__tht_phase_started__:F9_DO_NOT_FORWARD",
+  });
+
+  expect(seen).toEqual([{ type: "system_event", event: "phase_started", phase: "F2" }]);
+  expect(JSON.stringify(seen)).not.toContain("DO_NOT_FORWARD");
+});
+
 test("assistant message_end exposes sanitized token usage with the configured context window", () => {
   const { rpc, fire } = fakeRpc();
   const bridge = new SessionBridge(rpc);