deleting a conversation forgets what the platform stored about it

Found by a sanity check after two commanders were deleted through the UI: the Command HQ tables cascaded
perfectly and four OTHER tables kept a row each, for ever. 24 orphaned rows in chat_session_models, 26 in
chat_session_events, against 14 live transcripts.

Nothing cascades because there is nothing to cascade FROM. All four are keyed on a transcript id, and a
transcript is a file the harness writes — there is no row for a conversation, so the database cannot help and
the delete path has to be explicit. It was not.

Three of the four are inert: a model, a bell preference, a durable copy of turn output nothing will ask for
again. `nudges` is not — it is a SCHEDULE, read by the tick in nudger.ts. A nudge belonging to a deleted
conversation is a timer that keeps firing at something that no longer exists. That is what turned this from
untidy into worth doing now.

deleteClaudeSession returns the IDS it removed rather than a boolean, because a `/clear` chain is several
transcripts presenting as one conversation and forgetting the head while orphaning its parts is the same bug
at a smaller scale.

THE TRAP THAT CHANGE INTRODUCED, caught before shipping: every call site said `if (deleteClaudeSession(...))`
and an empty array is TRUTHY in JavaScript, so a delete that found nothing would have reported success. The
typecheck was clean — `string[]` is a perfectly good truthy expression. All three sites test `.length` now.
Fifth silently-wrong thing today that a typecheck could not see.

Cleared the existing orphans with the same function the delete path now uses, after checking the one thing
that would have made it wrong: whether any of them belonged to a member, whose transcripts live in a home
this scan does not read. There is one account on this machine, so they were all the owner's.

Two chat_session_events rows appeared again immediately after, and are not a leak: the durable log is written
independently of the transcript — that is what makes turn output survive officer being down — so a session
that has just begun legitimately has events before a transcript exists.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/servers/api/chat/chat.ts

@@ -12,6 +12,7 @@ import {
   getChatNotifyPreference,
   getChatNotifyPreferences,
   setChatNotifyPreference,
+  forgetChatSessions,
 } from 'officerdb';
 import type { NotifyPreference } from 'officerdb/types';
 import { setNudge, getNudge, cancelNudge } from 'officerdb';
@@ -376,8 +377,21 @@ chatRouter.delete('/sessions/:id', async (ctx) => {
   const id = ctx.req.param('id');
   const cwd = cwdOf(ctx, who.home);
   if (isOpenCodeSessionId(id) && !who.isOwner) return ctx.text('Not found', 404);
-  const ok = isOpenCodeSessionId(id) ? await deleteOpenCodeSession(id) : deleteClaudeSession(who, cwd, id);
-  if (!ok) return ctx.text('Not found', 404);
+  if (isOpenCodeSessionId(id)) {
+    if (!(await deleteOpenCodeSession(id))) return ctx.text('Not found', 404);
+    return ctx.json({ ok: true });
+  }
+
+  // `.length`, not truthiness: this returns the IDS it removed and an empty array is truthy in JavaScript,
+  // so `if (removed)` would report a delete that found nothing as a success.
+  const removed = deleteClaudeSession(who, cwd, id);
+  if (!removed.length) return ctx.text('Not found', 404);
+
+  // The transcript is gone; forget what the platform stored ABOUT it. Four tables are keyed on a transcript
+  // id with no foreign key — there is no row for a conversation to reference — so nothing cascades and this
+  // has to be explicit. One of them, `nudges`, is a live schedule: left behind it keeps firing at a
+  // conversation that no longer exists.
+  await forgetChatSessions(removed);
   return ctx.json({ ok: true });
 });