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/data/harness-prompts.ts

@@ -258,9 +258,20 @@ update_memory and update_instructions save to this workspace by default: what yo
 export const SessionNamePrompt = `Name and summarize this conversation from its first exchange. Answer with a JSON object only, no markdown fence and no other text:
 {"title": "...", "summary": "..."}
 
-- title: what the conversation is about, at most 60 characters, no quotes and no trailing period. Say what the user wanted, not that it is a conversation.
+- title: what the conversation is about, at most 60 characters, no quotes and no trailing period. Say what the user wanted, not that it is a conversation. When it opens with a summary of an earlier session, name what this one carries on with, not every topic the summary recaps.
 - summary: what the user wanted and what was done so far. Keep names, numbers, paths and links exactly. Plain markdown bullets, no preamble.`;
 
+/**
+ * Asks the text model to carry a conversation into a new session when the
+ * user asks to (Continue in new session): what the bot itself writes with
+ * `continue_in_new_session`.
+ */
+export const SessionContinuePrompt = `This conversation is moving into a new session: only what you write now carries over, so whoever picks it up must be able to go on from it alone. Answer with a JSON object only, no markdown fence and no other text:
+{"title": "...", "summary": "..."}
+
+- title: what the new session carries on with, at most 60 characters, no quotes and no trailing period.
+- summary: what the user wants, decisions made, what's done, what's in progress or still open, and every name, number, path, link and ref ([bot:ID], [file:ID], ...) exactly. Plain markdown bullets, no preamble.`;
+
 /**
  * Asks the text model for a closed session's summary, carried into the
  * next session's prompt. Used when the session's own summary is stale
@@ -268,9 +279,18 @@ export const SessionNamePrompt = `Name and summarize this conversation from its
  */
 export const SessionSummaryPrompt = `Summarize this conversation for whoever picks it up next: what the user wanted, what was done, decisions made, open questions and anything still in progress. Keep names, numbers, paths and links exactly. Plain markdown bullets, no preamble.`;
 
+/**
+ * Told to a reply once its session is long: offer to move on.
+ */
+export function longSessionNote({ messages, max }: { messages: number; max: number }) {
+    return `# Long session
+
+This session has ${messages} messages (a new one starts on its own after ${max}). Every reply re-reads the recent ones, so each costs more as it grows. When the current topic reaches a natural break, or the user moves on to something new, carry the conversation into a fresh session with continue_in_new_session and say so in your answer.`;
+}
+
 /**
  * Heads the previous session's summary in a bot's prompt.
  */
 export const PreviousSessionNote = `# Earlier in this conversation
 
-This session carries on from an earlier one. What happened there:`;
+This session carries on from an earlier one. Only this summary of it is in front of you; when you need more (an exact figure, a link, what was agreed), look it up with search_past_sessions and read_past_session instead of guessing. What happened there:`;