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>

protocol.go

@@ -28,6 +28,7 @@ type SessionInfo struct {
 	Preview      string     `json:"preview"`
 	Workspace    string     `json:"workspace"`
 	Label        string     `json:"label,omitempty"`
+	WaitType     string     `json:"wait_type,omitempty"`
 	WaitingSince *time.Time `json:"waiting_since,omitempty"`
 }