fix(status): status save no longer fails on Synapse's 1-per-10s presence limit

Reported: 'Failed to save status — server may be rate limiting. Try again.'
on the first status change in a month. Root cause: Synapse rate-limits
PUT /presence/{user}/status to ONE request per 10 s per user by default
(rc_presence.per_user: per_second 0.1, burst_count 1), shared across all of
the user's devices, and our presence heartbeat (online/away on visibility and
activity changes, from every open tab/device) spends that budget — so a manual
save that lands within 10 s of a heartbeat gets a 429, which the form showed
as a dead end.

Two fixes: (1) the status save waits out Retry-After (bounded to ~25 s) via
setPresenceWithRetry instead of failing, and the error text now says what
actually happened (rate limit / server text / offline); (2) the heartbeat
dedupes — it only sends when presence or status actually changes (/sync
already keeps us online), so it stops burning the budget in the first place.
Unit-tested; reproduced headless with a routed 10 s limiter: heartbeat ok →
save 429 → retried 8 s later → saved.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/app/features/settings/account/Profile.tsx

@@ -38,6 +38,7 @@ import { SettingTile } from '../../../components/setting-tile';
 import { useMatrixClient } from '../../../hooks/useMatrixClient';
 import { getAccountData, setAccountData } from '../../../utils/accountData';
 import { presenceStateFromSetting } from '../../../hooks/usePresenceUpdater';
+import { describePresenceError, setPresenceWithRetry } from '../../../utils/presenceWrite';
 import { useSetting } from '../../../state/hooks/settings';
 import { settingsAtom } from '../../../state/settings';
 import { UserProfile, useUserProfile } from '../../../hooks/useUserProfile';
@@ -424,7 +425,10 @@ function ProfileStatus() {
   const [saveState, saveStatus] = useAsyncCallback(
     useCallback(
       (msg: string) =>
-        mx.setPresence({
+        // Synapse allows ONE presence write per 10 s per user (shared by all
+        // devices) and our heartbeat spends that budget too — wait out a 429
+        // instead of failing the user's save.
+        setPresenceWithRetry(mx, {
           // Derive presence from the user's chosen setting so writing a status
           // never overrides Invisible/DND/Idle (e.g. outing an Invisible user).
           presence: presenceStateFromSetting(presenceStatus, hidePresence),
@@ -690,7 +694,7 @@ function ProfileStatus() {
         </Box>
         {saveState.status === AsyncStatus.Error && (
           <Text size="T200" style={{ color: color.Critical.Main }}>
-            Failed to save status — server may be rate limiting. Try again.
+            {describePresenceError(saveState.error)}
           </Text>
         )}
         <Box alignItems="Center" gap="200">