feat: centralize session state on terminal server

- Add SessionStateManager (server/services/session-state.ts) as source
  of truth for agent status, tools, approvals, and notifications
- Integrate into terminal server with state patches broadcast via WS
- Add /add-approval and /resolve-approval endpoints so approval
  lifecycle is tracked centrally and broadcast to all clients
- Add permissionMode field to AgentSessionState
- Frontend store (session-state.ts) + WS service (session-state-ws.ts)
  consume snapshots and patches from terminal server (4103)
- Rewrite useGlobalApproval to derive pending approvals from
  centralized state — resolving on one client now clears all others
- Migrate useTranscriptDebug: processing, hookMeta, serverRegistry
  now derived from session state store; remove 5s registry polling
- hooks-approval.ts notifies terminal server on add/resolve

frontend/src/stores/session-state.ts

@@ -0,0 +1,208 @@
+import { defineStore } from 'pinia'
+import { ref, computed } from 'vue'
+
+// ── Types (mirror server/services/session-state.ts) ──
+
+export type AgentStatus =
+  | 'idle'
+  | 'processing'
+  | 'reading'
+  | 'writing'
+  | 'toolUse'
+  | 'toolDone'
+  | 'permissionRequest'
+  | 'notification'
+  | 'sessionStart'
+
+export interface ActiveTool {
+  name: string
+  input: unknown
+  startedAt: number
+}
+
+export interface PendingApproval {
+  requestId: string
+  type: 'permission' | 'plan'
+  toolName?: string
+  toolInput?: unknown
+  cwd?: string
+  lastAssistantText?: string
+  timestamp: number
+}
+
+export interface SessionNotification {
+  id: string
+  event: string
+  title: string
+  detail: string
+  type: 'info' | 'success' | 'warning' | 'error'
+  timestamp: number
+  persistent: boolean
+  expiresAt: number | null
+}
+
+export interface AgentTerminalInfo {
+  ptySessionId: string | null
+  alive: boolean
+  bufferSize: number
+  connectedClients: number
+}
+
+export interface AgentSessionState {
+  agent: string
+  sessionId: string | null
+  model: string | null
+  cwd: string | null
+  transcriptPath: string | null
+  permissionMode: string | null
+  status: AgentStatus
+  currentTool: ActiveTool | null
+  lastActivity: number
+  lastStopResponse: string | null
+  pendingApprovals: PendingApproval[]
+  terminal: AgentTerminalInfo
+  notifications: SessionNotification[]
+}
+
+// WS message types
+interface SessionStateSnapshot {
+  type: 'session-state-snapshot'
+  agents: Record<string, AgentSessionState>
+}
+
+interface SessionStatePatch {
+  type: 'session-state-patch'
+  agent: string
+  patch: Partial<AgentSessionState>
+  event: string
+  timestamp: number
+}
+
+interface TerminalRegistryChange {
+  type: 'terminal-registry-change'
+  registry: TerminalRegistryEntry[]
+  timestamp: number
+}
+
+export interface TerminalRegistryEntry {
+  ephemeralSessionId: string
+  transcriptSessionId: string
+  agent: string
+  label: string
+  command: string
+  createdAt: string
+  alive: boolean
+  clients: number
+  bufferSize: number
+}
+
+type SessionStateMessage = SessionStateSnapshot | SessionStatePatch | TerminalRegistryChange
+
+// ── Store ──
+
+export const useSessionState = defineStore('session-state', () => {
+  const agents = ref<Record<string, AgentSessionState>>({})
+  const terminalRegistry = ref<TerminalRegistryEntry[]>([])
+  const connected = ref(false)
+  const lastUpdate = ref(0)
+
+  // ── Computed helpers ──
+
+  const agentList = computed(() => Object.values(agents.value))
+
+  const agentNames = computed(() => Object.keys(agents.value))
+
+  function getAgent(name: string) {
+    return computed(() => agents.value[name] ?? null)
+  }
+
+  const anyPendingApprovals = computed(() =>
+    agentList.value.some(a => a.pendingApprovals.length > 0)
+  )
+
+  const totalPendingApprovals = computed(() =>
+    agentList.value.reduce((sum, a) => sum + a.pendingApprovals.length, 0)
+  )
+
+  const allPendingApprovals = computed(() =>
+    agentList.value.flatMap(a =>
+      a.pendingApprovals.map(p => ({ ...p, agent: a.agent }))
+    )
+  )
+
+  const visibleNotifications = computed(() => {
+    const now = Date.now()
+    return agentList.value
+      .flatMap(a => a.notifications.map(n => ({ ...n, agent: a.agent })))
+      .filter(n => n.persistent || !n.expiresAt || n.expiresAt > now)
+      .sort((a, b) => b.timestamp - a.timestamp)
+      .slice(0, 10)
+  })
+
+  // ── Message handler ──
+
+  function handleMessage(msg: SessionStateMessage) {
+    if (msg.type === 'session-state-snapshot') {
+      agents.value = { ...msg.agents }
+      lastUpdate.value = Date.now()
+    } else if (msg.type === 'session-state-patch') {
+      const current = agents.value[msg.agent]
+      if (current) {
+        agents.value = {
+          ...agents.value,
+          [msg.agent]: { ...current, ...msg.patch }
+        }
+      } else {
+        // New agent appeared — treat patch as full state if it has required fields
+        agents.value = {
+          ...agents.value,
+          [msg.agent]: msg.patch as AgentSessionState
+        }
+      }
+      lastUpdate.value = msg.timestamp
+    } else if (msg.type === 'terminal-registry-change') {
+      terminalRegistry.value = msg.registry
+      lastUpdate.value = msg.timestamp
+    }
+  }
+
+  // ── Actions ──
+
+  async function respondApproval(requestId: string, decision: string, reason?: string) {
+    await fetch('/api/hooks-approval/respond', {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ requestId, decision, reason })
+    })
+  }
+
+  async function respondPlanApproval(requestId: string, decision: string, reason?: string) {
+    await fetch('/api/hooks-approval/respond-plan', {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ requestId, decision, reason })
+    })
+  }
+
+  function setConnected(value: boolean) {
+    connected.value = value
+  }
+
+  return {
+    agents,
+    terminalRegistry,
+    connected,
+    lastUpdate,
+    agentList,
+    agentNames,
+    getAgent,
+    anyPendingApprovals,
+    totalPendingApprovals,
+    allPendingApprovals,
+    visibleNotifications,
+    handleMessage,
+    respondApproval,
+    respondPlanApproval,
+    setConnected,
+  }
+})