docs(webui): document slash command lifecycles

webui/src/lib/types.ts

@@ -781,6 +781,15 @@ export interface TranscriptionSettingsUpdate {
   maxUploadMb: number;
 }
 
+/**
+ * Backend-owned contract for how a slash command affects WebUI turn state.
+ *
+ * - side_channel: returns control text without starting or ending an agent turn.
+ * - finalize_active_turn: side-channel command that also closes the active UI turn.
+ * - stop_active_turn: cancels the active turn; exact submits may be intercepted locally.
+ * - agent_turn: always enters the normal agent path.
+ * - agent_turn_with_args: no args is side-channel usage; args enter the agent path.
+ */
 export type SlashCommandLifecycle =
   | "side_channel"
   | "finalize_active_turn"