fix: stop tracking sessions that never become ready

When session readiness times out, immediately close the spawned pane and skip tracking to prevent stale mappings from causing reopen and close anomalies.

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

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

src/features/tmux-subagent/manager.test.ts

@@ -434,6 +434,53 @@ describe('TmuxSessionManager', () => {
   })
 
   describe('onSessionDeleted', () => {
+    test('does not track session when readiness timed out', async () => {
+      // given
+      mockIsInsideTmux.mockReturnValue(true)
+      let stateCallCount = 0
+      mockQueryWindowState.mockImplementation(async () => {
+        stateCallCount++
+        if (stateCallCount === 1) {
+          return createWindowState()
+        }
+        return createWindowState({
+          agentPanes: [
+            {
+              paneId: '%mock',
+              width: 40,
+              height: 44,
+              left: 100,
+              top: 0,
+              title: 'omo-subagent-Timeout Task',
+              isActive: false,
+            },
+          ],
+        })
+      })
+
+      const { TmuxSessionManager } = await import('./manager')
+      const ctx = createMockContext({ sessionStatusResult: { data: {} } })
+      const config: TmuxConfig = {
+        enabled: true,
+        layout: 'main-vertical',
+        main_pane_size: 60,
+        main_pane_min_width: 80,
+        agent_pane_min_width: 40,
+      }
+      const manager = new TmuxSessionManager(ctx, config, mockTmuxDeps)
+
+      await manager.onSessionCreated(
+        createSessionCreatedEvent('ses_timeout', 'ses_parent', 'Timeout Task')
+      )
+      mockExecuteAction.mockClear()
+
+      // when
+      await manager.onSessionDeleted({ sessionID: 'ses_timeout' })
+
+      // then
+      expect(mockExecuteAction).toHaveBeenCalledTimes(0)
+    })
+
     test('closes pane when tracked session is deleted', async () => {
       // given
       mockIsInsideTmux.mockReturnValue(true)
@@ -521,8 +568,13 @@ describe('TmuxSessionManager', () => {
       mockIsInsideTmux.mockReturnValue(true)
 
       let callCount = 0
-      mockExecuteActions.mockImplementation(async () => {
+      mockExecuteActions.mockImplementation(async (actions) => {
         callCount++
+        for (const action of actions) {
+          if (action.type === 'spawn') {
+            trackedSessions.add(action.sessionId)
+          }
+        }
         return {
           success: true,
           spawnedPaneId: `%${callCount}`,