extract sync orchestration into sync.js, unify on sync.tick heartbeat

caldav.js was carrying the core sync timer, autosync toggle, relay
settings and every poller hook alongside its actual CalDAV/calendar
config concerns. Split out:

- New sync.js owns the single background timer, header Sync button,
  autosync pause toggle, configurable interval, and emits `sync.tick`
  so plugins can fan out without their own setIntervals.
- collab-buckets + chat now subscribe to sync.tick instead of running
  their own pollers, so the manual Sync button refreshes them too and
  the Autosync pause actually pauses everything.
- Replace the number input for sync interval with a stepped slider
  (5s..1h snap points) and a live label, bumped to 1.9.2.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

public/plugins/chat/chat.js

@@ -410,6 +410,12 @@ function init() {
             restartPoll();
         }
     });
+
+    // Also refresh on the global sync heartbeat. Our own timer keeps
+    // the faster flyout-open cadence (UX-specific); tick guarantees
+    // that the header Sync button refreshes chat too, even when the
+    // flyout is closed and our own timer sits at 20s.
+    hyprcrd.hooks?.on?.('sync.tick', () => { pollOnce().catch(() => {}); });
 }
 
 if (document.readyState === 'loading') {

public/plugins/collab-buckets/collab-buckets.js

@@ -4,9 +4,9 @@
 // rows in the standard bucket bar. The plugin just owns the sync + the
 // visual unread-state decoration:
 //
-//  - Polls /api/collab-buckets/poll every POLL_INTERVAL_MS. The backend
-//    mirrors each remote bucket into the main `buckets` table so the core
-//    bucket bar renders it automatically.
+//  - Polls /api/collab-buckets/poll on every `sync.tick` (shared timer
+//    in sync.js). The backend mirrors each remote bucket into the main
+//    `buckets` table so the core bucket bar renders it automatically.
 //  - Exposes `window._collabBucketsCreateDialog` — an async function that
 //    the core + Bucket button calls so we can pop a richer "new bucket"
 //    modal with an optional "collaborative" checkbox + member picker.
@@ -26,14 +26,9 @@ const $ = (id) => document.getElementById(id);
 let collabByUid = new Map();
 // card_id (number) -> true for cards with foreign edits we haven't opened yet
 let unreadCards = new Set();
-let pollHandle = null;
-// The core CalDAV/relay sync cadence (Settings → Relay → Sync frequency,
-// default 15s) also drives the collab poll. Users can dial up or down
-// without touching code. Defaults + clamp mirror the core helper.
-function getPollIntervalMs() {
-    const v = parseInt(localStorage.getItem('hyprcrd-sync-interval-sec'));
-    return (Number.isFinite(v) && v >= 5 ? v : 15) * 1000;
-}
+// Collab card sync is driven by the shared `sync.tick` hook from
+// sync.js — one timer fans out to every plugin poller, the central
+// timer honors the Autosync pause for us.
 
 // Phase 4: edit locks (now exclusive — server-enforced)
 // card_uid -> { bucket_uid, holder_username, expires_at }
@@ -171,24 +166,11 @@ function showQueuedToast(message) {
     setTimeout(() => { toast.classList.add('fade-out'); setTimeout(() => toast.remove(), 400); }, 6000);
 }
 
-function startPolling() {
-    stopPolling();
-    pollHandle = setInterval(pollOnce, getPollIntervalMs());
-}
-function stopPolling() {
-    if (pollHandle) { clearInterval(pollHandle); pollHandle = null; }
-}
-
-// Restart when the user changes the sync interval in settings.
-hyprcrd.hooks?.on?.('sync.interval.changed', () => {
-    if (pollHandle) startPolling();
-});
-
-// Pause / resume alongside the header autosync toggle.
-hyprcrd.hooks?.on?.('autosync.changed', (on) => {
-    if (on) startPolling();
-    else    stopPolling();
-});
+// Subscribe to the global sync heartbeat. The central timer in sync.js
+// honors the Autosync pause + the configurable interval for us, and
+// the header Sync button emits the same tick so manual sync pushes
+// collab cards too.
+hyprcrd.hooks?.on?.('sync.tick', () => { pollOnce().catch(() => {}); });
 
 // ── Bucket bar decoration ─────────────────────────────────────────
 
@@ -992,9 +974,8 @@ async function init() {
     decorateBucketBar();
     decorateBoardLocks();
     decorateBoardUnread();
-    // Respect the header autosync toggle — if the user has paused it,
-    // skip the recurring poll entirely. Hook above restarts when toggled.
-    if (localStorage.getItem('hyprcrd-autosync-enabled') !== '0') startPolling();
+    // No local timer: subsequent polls come from the global `sync.tick`
+    // hook (central timer in sync.js honors Autosync pause + interval).
 }
 
 // Defer init until the CSRF token is live — `checkAuth()` sets it async on

public/plugins/tests/runner.js

@@ -5,7 +5,7 @@
 // Backup is created before and auto-restored after every run.
 
 import { getCsrf } from '../../js/modules/util.js';
-import { stopBackgroundSync, startBackgroundSync } from '../../js/modules/caldav.js';
+import { stopBackgroundSync, startBackgroundSync } from '../../js/modules/sync.js';
 
 // Suites live on window so two runner.js instances (one cached and loaded
 // by test files via bare imports, one fresh and loaded by loader.js with