fix(todo-continuation): cancel stale ULW countdown

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/hooks/todo-continuation-enforcer/non-idle-events.test.ts

@@ -67,4 +67,35 @@ describe("handleNonIdleEvent", () => {
     expect(state.wasCancelled).toBe(true)
     expect(state.tokenLimitDetected).toBe(true)
   })
+
+  test("given ultrawork loop continuation user message update, cancels stale todo continuation countdown", () => {
+    // given
+    const sessionID = "ses_ulw_todo_overlap"
+    const state = sessionStateStore.getState(sessionID)
+    state.countdownStartedAt = Date.now() - 10_000
+    state.wasCancelled = true
+    state.tokenLimitDetected = true
+
+    // when
+    handleNonIdleEvent({
+      eventType: "message.updated",
+      properties: {
+        sessionID,
+        info: { role: "user" },
+        parts: [
+          {
+            type: "text",
+            text: `ultrawork [SYSTEM DIRECTIVE: OH-MY-OPENCODE - RALPH LOOP 2/500]\ncontinue\n${OMO_INTERNAL_INITIATOR_MARKER}`,
+            synthetic: true,
+          },
+        ],
+      },
+      sessionStateStore,
+    })
+
+    // then
+    expect(state.countdownStartedAt).toBeUndefined()
+    expect(state.wasCancelled).toBe(true)
+    expect(state.tokenLimitDetected).toBe(true)
+  })
 })