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/pages/admin/settings/(functions)/grab-settings-server-props.ts

@@ -8,6 +8,7 @@ import type { BunextPageServerFn } from "@moduletrace/bunext/types";
 import grabRunLimitsOverview from "@/src/functions/backend/db/app-settings/grab-run-limits";
 import grabSkillLimitsOverview from "@/src/functions/backend/db/app-settings/grab-skill-limits";
 import grabHookCallRetentionOverview from "@/src/functions/backend/db/app-settings/grab-hook-events-keep-days";
+import grabSessionLengthOverview from "@/src/functions/backend/db/app-settings/grab-bot-session-max-messages";
 import grabStorageQuotaOverview from "@/src/functions/backend/db/app-settings/grab-storage-quota-overview";
 import { grabSystemPromptAppendOverview } from "@/src/functions/backend/db/app-settings/grab-system-prompt-append";
 import runningVersion from "@/src/utils/running-version";
@@ -51,6 +52,7 @@ export default async function grabSettingsServerProps({ req }: Params) {
             run_limits: await grabRunLimitsOverview().catch(() => null),
             skill_limits: await grabSkillLimitsOverview().catch(() => null),
             hook_call_retention: await grabHookCallRetentionOverview().catch(() => null),
+            session_length: await grabSessionLengthOverview().catch(() => null),
             running_version: runningVersion({ env: process.env }),
         },
     };