feat(03-01): HookEvent struct, processHookEvent mapping, UpdateFromHook, WaitType

- HookEvent struct parses Claude Code hook JSON payload
- processHookEvent maps Notification/Stop/PostToolUse/PreToolUse to State+WaitType
- UpdateFromHook creates new entries and manages WaitingSince transitions
- SessionInfo.WaitType serialized in JSON with omitempty
- 12 tests cover all event mappings, edge cases, and JSON serialization

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

hook.go

@@ -0,0 +1,83 @@
+package main
+
+import "time"
+
+// HookEvent represents the JSON payload sent by Claude Code hooks.
+type HookEvent struct {
+	SessionID        string `json:"session_id"`
+	TranscriptPath   string `json:"transcript_path,omitempty"`
+	Cwd              string `json:"cwd,omitempty"`
+	HookEventName    string `json:"hook_event_name"`
+	NotificationType string `json:"notification_type,omitempty"`
+	Message          string `json:"message,omitempty"`
+	Title            string `json:"title,omitempty"`
+	LastAssistantMsg string `json:"last_assistant_message,omitempty"`
+	StopHookActive   bool   `json:"stop_hook_active,omitempty"`
+	ToolName         string `json:"tool_name,omitempty"`
+}
+
+// processHookEvent maps a Claude Code hook event to a registry update.
+// Ignores empty session IDs and unknown event types.
+func (d *Daemon) processHookEvent(event HookEvent) {
+	if event.SessionID == "" {
+		return
+	}
+
+	var state, waitType string
+
+	switch event.HookEventName {
+	case "Notification":
+		state = "Needs Input"
+		switch event.NotificationType {
+		case "permission_prompt":
+			waitType = "permission"
+		case "idle_prompt":
+			waitType = "idle"
+		default:
+			waitType = "question"
+		}
+	case "Stop":
+		state = "Needs Input"
+		waitType = "question"
+	case "PostToolUse", "PreToolUse":
+		state = "Working"
+		waitType = ""
+	default:
+		return
+	}
+
+	d.registry.UpdateFromHook(event.SessionID, state, waitType, event.Cwd)
+}
+
+// UpdateFromHook updates a session from a hook event.
+// Creates the entry if it doesn't exist yet (hook can arrive before first poll).
+func (r *SessionRegistry) UpdateFromHook(sessionID, state, waitType, cwd string) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	existing, ok := r.sessions[sessionID]
+	if !ok {
+		existing = &TrackedSession{}
+		r.sessions[sessionID] = existing
+	}
+
+	prevState := existing.PrevState
+	existing.Info.SessionID = sessionID
+	existing.Info.State = state
+	existing.Info.WaitType = waitType
+	if cwd != "" {
+		existing.Info.Cwd = cwd
+	}
+
+	// WaitingSince transition
+	isWaiting := state == "Needs Input"
+	wasWaiting := prevState == "Needs Input"
+	if isWaiting && !wasWaiting {
+		now := time.Now()
+		existing.Info.WaitingSince = &now
+	} else if !isWaiting {
+		existing.Info.WaitingSince = nil
+	}
+
+	existing.PrevState = state
+}