fix: keep supervisor controls usable and prevent overlapping reviews

Allow only one active review across manual starts, automatic runs and resume. Add cancellation that holds admission through runtime cleanup, preserves saved batches and prevents cancelled runs from resuming.

Keep review controls usable during execution, show a dismissible progress notice and remove redundant filter labels. Include focused regressions and lifecycle documentation.

Release note: Supervision reviews can now be cancelled from Activity records. Starting another review shows the active review instead of duplicating work, while scope, time and refresh controls remain available.

src/main/ipc.test.ts

@@ -5896,6 +5896,54 @@ describe('registerIpcHandlers agent terminal state', () => {
     } finally { finish(); await harness.dispose(); database.close(); vi.useRealTimers() }
   })
 
+  it('production supervision IPC cancels the runtime and holds admission until conversation cleanup settles', async () => {
+    const database = new AssistantDatabase(':memory:')
+    database.initialize(process.cwd())
+    const now = Date.now()
+    database.saveLocalConversations([{ header: { id: crypto.randomUUID(), projectId: database.listProjects()[0]!.id, title: 'Cancel review', updatedAt: now },
+      messages: [{ id: crypto.randomUUID(), role: 'user', state: 'complete', content: 'Review this', createdAt: now }] }])
+    let entered!: () => void, cleaning!: () => void, finish!: () => void
+    const started = new Promise<void>(resolve => { entered = resolve })
+    const cleanupStarted = new Promise<void>(resolve => { cleaning = resolve })
+    const cleanup = new Promise<void>(resolve => { finish = resolve })
+    const run = vi.fn(async function* (_input: AgentExecutionRequest, signal: AbortSignal) {
+      entered()
+      await new Promise<void>(resolve => signal.addEventListener('abort', () => resolve(), { once: true }))
+      signal.throwIfAborted()
+      yield { type: 'done' as const, requestId: _input.requestId }
+    })
+    const releaseConversation = vi.fn(async () => { cleaning(); await cleanup })
+    const harness = createHarness({ runtimeId: 'model', capability: 'chat', run, releaseConversation }, undefined, 'always', undefined, false,
+      undefined, undefined, undefined, false, undefined, undefined, undefined, undefined, database)
+    try {
+      harness.getApplicationSettings.mockResolvedValue({ heartbeatEnabled: true })
+      const event = trustedEvent(harness.webContents)
+      const request = { trigger: 'manual', scope: { kind: 'global' }, timeRange: {
+        from: new Date(now - 1).toISOString(), to: new Date(now + 1).toISOString()
+      } }
+      const pending = electronMocks.handlers.get(ipcChannels.supervisionRun)!(event, request)
+      await started
+      const runId = database.listSupervisionActivity()[0]!.id
+      const input = { runId }
+      await expect(electronMocks.handlers.get(ipcChannels.supervisionCancel)!({ sender: {} }, input)).rejects.toThrow()
+      await expect(electronMocks.handlers.get(ipcChannels.supervisionCancel)!(event, { runId: 'invalid' })).rejects.toThrow()
+      const cancellation = electronMocks.handlers.get(ipcChannels.supervisionCancel)!(event, input)
+      await cleanupStarted
+      expect(database.listSupervisionActivity()[0]!.status).toBe('cancelled')
+      expect(electronMocks.handlers.get(ipcChannels.supervisionExecution)!(event)).toEqual({ active: true, runId, stopping: 'cancelled' })
+      await expect(electronMocks.handlers.get(ipcChannels.supervisionRun)!(event, request)).rejects.toThrow('SUPERVISION_REVIEW_BUSY')
+      await expect(electronMocks.handlers.get(ipcChannels.supervisionResume)!(event, input)).rejects.toThrow('SUPERVISION_REVIEW_BUSY')
+      finish()
+      await cancellation
+      await expect(pending).resolves.toMatchObject({ status: 'cancelled' })
+      expect(electronMocks.handlers.get(ipcChannels.supervisionExecution)!(event)).toMatchObject({ active: false })
+      await expect(electronMocks.handlers.get(ipcChannels.supervisionResume)!(event, input)).rejects.toThrow('SUPERVISION_REVIEW_CANCELLED')
+      expect(database.listSupervisionResults()).toEqual([])
+      expect(run).toHaveBeenCalledTimes(1)
+      expect(releaseConversation).toHaveBeenCalledTimes(1)
+    } finally { finish(); await harness.dispose(); database.close() }
+  })
+
   it('production supervision IPC pauses in-flight work and resumes saved batches without replaying them', async () => {
     const database = new AssistantDatabase(':memory:')
     database.initialize(process.cwd())