fix(schedule): load scheduled messages from the server; offer to cancel them at logout (#322)

The tray only knew what this browser had scheduled (localStorage), but
Synapse lists every pending one via MSC4140 GET /delayed_events. Load it
when the tray mounts and on window focus (localStorage stays as a first-
paint cache), keeping only non-state m.room.message events. Logout now
says "N scheduled messages still send after you log out" and offers to
cancel them.

Fixes #322

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

src/app/utils/scheduledMessages.ts

@@ -1,4 +1,5 @@
 import { IContent, MatrixClient, Method } from 'matrix-js-sdk';
+import type { ScheduledMessage } from '../state/scheduledMessages';
 
 /**
  * Schedule a message via MSC4140 (delayed messages).
@@ -76,3 +77,61 @@ export async function sendScheduledMessageNow(mx: MatrixClient, delayId: string)
     { prefix: '/_matrix/client/unstable/org.matrix.msc4140' },
   );
 }
+
+type DelayedEventItem = {
+  delay_id?: unknown;
+  room_id?: unknown;
+  type?: unknown;
+  state_key?: unknown;
+  content?: unknown;
+  delay?: unknown;
+  delay_ms?: unknown;
+  running_since?: unknown;
+  delayed_since_ts?: unknown;
+};
+
+/**
+ * [Gitea #322] Pure: the user's pending scheduled messages from an MSC4140
+ * `GET /delayed_events` response. Synapse answers `{ delayed_events: [...] }`;
+ * the current MSC shape is `{ scheduled: [...] }`. Call-membership delayed
+ * events share the endpoint, so only non-state `m.room.message`s are kept.
+ */
+export function parseDelayedEvents(res: unknown): ScheduledMessage[] {
+  if (!res || typeof res !== 'object') return [];
+  const r = res as { delayed_events?: unknown; scheduled?: unknown };
+  const list = Array.isArray(r.delayed_events) ? r.delayed_events : r.scheduled;
+  if (!Array.isArray(list)) return [];
+  const out: ScheduledMessage[] = [];
+  list.forEach((raw: DelayedEventItem) => {
+    if (!raw || typeof raw !== 'object') return;
+    if (raw.type !== 'm.room.message' || raw.state_key !== undefined) return;
+    if (typeof raw.delay_id !== 'string' || typeof raw.room_id !== 'string') return;
+    if (!raw.content || typeof raw.content !== 'object') return;
+    const delay = Number(raw.delay ?? raw.delay_ms);
+    const since = Number(raw.running_since ?? raw.delayed_since_ts);
+    if (!Number.isFinite(delay) || !Number.isFinite(since)) return;
+    out.push({
+      delayId: raw.delay_id,
+      roomId: raw.room_id,
+      content: raw.content as IContent,
+      sendAt: since + delay,
+    });
+  });
+  return out;
+}
+
+/** The user's pending scheduled messages, as the server has them. */
+export async function fetchScheduledMessages(mx: MatrixClient): Promise<ScheduledMessage[]> {
+  const res = await mx.http.authedRequest(Method.Get, '/delayed_events', undefined, undefined, {
+    prefix: '/_matrix/client/unstable/org.matrix.msc4140',
+  });
+  return parseDelayedEvents(res);
+}
+
+/** Group by room, the shape of `scheduledMessagesAtom`. */
+export function groupScheduledByRoom(msgs: ScheduledMessage[]): Map<string, ScheduledMessage[]> {
+  const map = new Map<string, ScheduledMessage[]>();
+  msgs.forEach((m) => map.set(m.roomId, [...(map.get(m.roomId) ?? []), m]));
+  map.forEach((list) => list.sort((a, b) => a.sendAt - b.sendAt));
+  return map;
+}