perf(tuner): idle the always-on tuner viz rAF when there's no signal (#647)

The v3 home tuner card runs continuously, and every tuner visualization
drove a self-rescheduling 60fps requestAnimationFrame loop that never
stopped — pinning a renderer core even on a silent home screen with the
needle/strobe at rest.

Make each viz idle its loop once there's nothing left to animate, and
re-kick it from update() on the next reading that actually moves it:

- analogue-gauge: stop when the needle + drum strip have settled on their
  targets (|target-current| below a sub-visible epsilon); restart when a
  new reading moves the target.
- strobe / mace-fx-iii / chef-mt3: stop when there's no live signal and the
  strobe drift (and glow fade) have fully decayed; restart on the next note.
- toilet-tuner: stop when silent and the plunger has eased back to centre;
  restart on the next reading (guarded so repeated no-signal updates don't
  re-kick a parked loop).

Active tuning is unchanged — the loop runs whenever a note is sounding or
the indicator is still moving. Bumps tuner 1.3.1 -> 1.3.2.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

plugins/tuner/visualization/toilet-tuner.js

@@ -122,6 +122,26 @@
             plungerEl.style.left = _leftPct.toFixed(2) + '%';
             plungerEl.style.top  = _topPct.toFixed(2)  + '%';
 
+            // No live signal and the plunger has eased back to its resting centre
+            // → idle the loop. update() re-kicks it on the next note.
+            if (_currentNote === null && !_plungerDipped
+                    && Math.abs(targetLeft - _leftPct) < 0.05) {
+                _leftPct = targetLeft;
+                plungerEl.style.left = _leftPct.toFixed(2) + '%';
+                _rafId = null;
+                _lastTime = null;
+                return;
+            }
+
+            _rafId = requestAnimationFrame(_animate);
+        }
+
+        function _kick() {
+            if (_rafId !== null) return;
+            // Already parked at rest with no signal → nothing to animate, stay idle.
+            if (_currentNote === null && !_plungerDipped
+                    && Math.abs(_TUNER_TT_CENTRE_PCT - _leftPct) < 0.05) return;
+            _lastTime = null;
             _rafId = requestAnimationFrame(_animate);
         }
 
@@ -130,6 +150,7 @@
             _currentNote  = note;
             _currentCents = note === null ? 0 : cents;
             if (!_plungerDipped) { noteEl.textContent = note || '–'; }
+            _kick();   // a new reading may move the plunger → ensure the loop runs
         }
 
         function destroy() {