Gate session ID liveness by shell foreground state

Once OSC 133;D proves a pane is back at the shell, don't return the
session ID even if a durable record survived the exit. This prevents
treating exited sessions as still active when the user is typing at
the prompt.

src/renderer/src/components/terminal-pane/pane-agent-session-id.test.ts

@@ -7,11 +7,13 @@ const PANE_KEY = 'tab-1:11111111-1111-4111-8111-111111111111'
 
 function state(
   live?: AgentStatusEntry,
-  sleeping?: SleepingAgentSessionRecord
+  sleeping?: SleepingAgentSessionRecord,
+  shellForeground = false
 ): PaneAgentSessionIdState {
   return {
     agentStatusByPaneKey: live ? { [PANE_KEY]: live } : {},
-    sleepingAgentSessionsByPaneKey: sleeping ? { [PANE_KEY]: sleeping } : {}
+    sleepingAgentSessionsByPaneKey: sleeping ? { [PANE_KEY]: sleeping } : {},
+    paneForegroundAgentByPaneKey: { [PANE_KEY]: { agent: 'claude', shellForeground } }
   }
 }
 
@@ -68,6 +70,39 @@ describe('resolvePaneAgentSessionId', () => {
     ).toBe('confirmed-session')
   })
 
+  describe('liveness', () => {
+    it('is absent once the pane is proven back at the shell', () => {
+      expect(
+        resolvePaneAgentSessionId(state(live('live-session'), undefined, true), PANE_KEY)
+      ).toBe(null)
+    })
+
+    it('is absent at the shell even when a durable record survives the exit', () => {
+      expect(
+        resolvePaneAgentSessionId(state(undefined, sleeping('sleeping-session'), true), PANE_KEY)
+      ).toBeNull()
+    })
+
+    it('keeps a session whose foreground evidence is only that an agent runs', () => {
+      expect(
+        resolvePaneAgentSessionId(state(live('live-session'), undefined, false), PANE_KEY)
+      ).toBe('live-session')
+    })
+
+    it('keeps a session for a pane with no foreground evidence at all', () => {
+      expect(
+        resolvePaneAgentSessionId(
+          {
+            agentStatusByPaneKey: { [PANE_KEY]: live('live-session') },
+            sleepingAgentSessionsByPaneKey: {},
+            paneForegroundAgentByPaneKey: {}
+          },
+          PANE_KEY
+        )
+      ).toBe('live-session')
+    })
+  })
+
   it('does not read identity from a sibling pane', () => {
     const sibling = 'tab-1:22222222-2222-4222-8222-222222222222'
     expect(resolvePaneAgentSessionId(state(undefined, sleeping('session-1')), sibling)).toBeNull()

src/renderer/src/components/terminal-pane/pane-agent-session-id.ts

@@ -1,16 +1,24 @@
 import type { AgentStatusEntry } from '../../../../shared/agent-status-types'
 import type { SleepingAgentSessionRecord } from '../../../../shared/agent-session-resume'
+import type { PaneForegroundAgentEntry } from '../../store/slices/pane-foreground-agent'
 
 export type PaneAgentSessionIdState = {
   agentStatusByPaneKey: Record<string, AgentStatusEntry | undefined>
   sleepingAgentSessionsByPaneKey: Record<string, SleepingAgentSessionRecord | undefined>
+  paneForegroundAgentByPaneKey: Record<string, PaneForegroundAgentEntry | undefined>
 }
 
-/** Resolves the provider session owned by one exact terminal pane. */
+/** Resolves the provider session owned by one exact terminal pane, while its agent is still live. */
 export function resolvePaneAgentSessionId(
   state: PaneAgentSessionIdState,
   paneKey: string
 ): string | null {
+  // OSC 133;D proves the pane is back at the shell. The durable record outlives that exit on
+  // purpose (cold restore resumes from it), so gate it here too — otherwise the gate would only
+  // hold for panes whose agent has no resumable record.
+  if (state.paneForegroundAgentByPaneKey[paneKey]?.shellForeground === true) {
+    return null
+  }
   const live = state.agentStatusByPaneKey[paneKey]
   if (live && live.restoredUnconfirmed !== true) {
     return live.providerSession?.id ?? null