Mark the session on screen as Current in the session lists

- The conversation page tells the rail and the sessions modal which
  session it shows (announceShownSession, useShownSession); they reload,
  so a session reopened by ?session_id= shows at once.
- Only that session is Current and greyed out (the active one without
  ?session_id=); the active row then leads back to it.
- The rail lists the session on screen even when it's older than its
  latest sessions.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/types/index.ts

@@ -1581,6 +1581,16 @@ export type ConversationExportSession = {
     created_at: number;
 };
 
+/**
+ * The session a conversation page shows (`cobble:session-shown`), told to
+ * the rail so it marks it.
+ */
+export type ShownSession = {
+    bot_id: number;
+    workspace_id: number | null;
+    session: BUN_SQLITE_COBBLE_BOT_SESSIONS;
+};
+
 export type ConversationHistoryPayload = {
     history?: ConversationHistory;
     redirect?: string;