fix(master): break effect_update_depth_exceeded loop in countdown

Two $effects were reading state they also wrote, turning each into its
own dependency:

- AutoCountdown reset effect: `now = tickStart` read tickStart after
  writing it. Use a local snapshot so neither rune is read post-write.
- MasterPanel auto-call effect: `tickCount++` read tickCount. Drop the
  bump here — AutoCountdown's reset effect already re-baselines on the
  rising edge of `running` and on `duration` change, so re-arms remain
  covered. handleDrawNext keeps its per-draw bump (not in effect scope).

web/src/lib/AutoCountdown.svelte

@@ -24,12 +24,15 @@
 
   // Re-baseline whenever the parent bumps tickKey, running flips on, or
   // duration changes mid-run (e.g. host moves the speed slider).
+  // Use a local snapshot so we don't read `tickStart` after writing it —
+  // that would make this effect depend on its own write and infinite-loop.
   $effect(() => {
     tickKey; // subscribe
     duration; // subscribe — keeps the contract explicit, not parent-coupled
     if (running) {
-      tickStart = performance.now();
-      now = tickStart;
+      const t = performance.now();
+      tickStart = t;
+      now = t;
     }
   });
 

web/src/lib/MasterPanel.svelte

@@ -123,12 +123,10 @@
       autoRunning = false;
       return;
     }
-    // Re-baseline countdown on every (re-)arm: rising edge of autoRunning,
-    // speed change, autoCallEnabled toggle. handleDrawNext bumps it again
-    // per tick so the ring re-fills before the next interval elapses.
-    // Safe self-write: this effect doesn't read tickCount, so the bump
-    // can't re-trigger it.
-    tickCount++;
+    // No tickCount bump here on purpose: `tickCount++` would read tickCount
+    // and turn this effect into its own dependency (effect_update_depth_exceeded).
+    // AutoCountdown's reset effect already re-baselines on `running` rising
+    // edge and on `duration` change, so re-arms are covered without our help.
     const ms = settings.autoCallSpeed * 1000;
     const id = setInterval(() => {
       if (!state || state.remaining.length === 0) {