Carry conversations into new sessions with a visible summary

- Bots get continue_in_new_session: the bot writes a title and summary,
  the session closes for good (read-only) and the new one opens with the
  summary as a "Carried over from the last session" message that links
  back to the old session.
- Continue in new session (conversation menu, sessions modal) and the
  automatic rollover at the session length do the same; New session now
  starts a fresh, unlinked session.
- Session length is an app setting in Settings > General.
- ?session_id= opens a session; a carried-over one shows a bar linking to
  where the conversation went on instead of the composer.
- The thread can open the previous session above the current one (shown
  only, never in the prompt), and replies get search_past_sessions and
  read_past_session.
- Sessions are named from their opening messages, not their latest, and
  a carried summary is labelled as the earlier session's.

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

src/utils/conversation-href.ts

@@ -0,0 +1,22 @@
+type Params = {
+    bot_id: number | string;
+    /**
+     * The workspace the conversation is in; none for the bot's own chat.
+     */
+    workspace_id?: number | string | null;
+    /**
+     * A session to show other than the active one.
+     */
+    session_id?: number | string | null;
+};
+
+/**
+ * The page of a conversation (`/admin/bots/<id>` or
+ * `/admin/workspaces/<id>/bots/<id>`), opened on one of its sessions when
+ * `session_id` is given.
+ */
+export default function conversationHref({ bot_id, workspace_id, session_id }: Params) {
+    const path = workspace_id ? `/admin/workspaces/${workspace_id}/bots/${bot_id}` : `/admin/bots/${bot_id}`;
+
+    return session_id ? `${path}?session_id=${session_id}` : path;
+}