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/mace-fx-iii.js

@@ -354,10 +354,19 @@
                 if (_smoothedCents > 0) { speed = -speed; }
                 _strobeOffset = ((_strobeOffset + speed * dt) % _totalDash + _totalDash) % _totalDash;
                 arcPath.setAttribute('stroke-dashoffset', String(_strobeOffset));
+            } else if (_currentCents === 0) {
+                // Fully decelerated and no live signal → idle the loop instead of
+                // rescheduling forever. update() re-kicks it on the next note.
+                _rafId = null;
+                _lastTime = null;
+                return;
             }
 
             _rafId = requestAnimationFrame(_animateStrobe);
         }
+        function _kick() {
+            if (_rafId === null) { _lastTime = null; _rafId = requestAnimationFrame(_animateStrobe); }
+        }
         _rafId = requestAnimationFrame(_animateStrobe);
 
         // ── Helper: derive octave number from frequency ───────────────
@@ -439,6 +448,7 @@
 
             // Strobe state — smoothed animation decelerates naturally when _currentCents → 0
             _currentCents = hasNote ? cents : 0;
+            if (hasNote) { _kick(); }   // new signal → restart the decel loop if idled
         }
 
         // ── Public: destroy ───────────────────────────────────────────