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/analogue-gauge.js

@@ -18,6 +18,8 @@
     // ── Constants ─────────────────────────────────────────────────────
     var _TUNER_LABEL_H = 12;           // px height of each drum label
     var _TUNER_NEEDLE_HALF_SWEEP = 90; // degrees — ±50 cents = horizontal (180° apart)
+    var _SETTLE_A = 0.05;              // deg — needle "settled" threshold (sub-visible)
+    var _SETTLE_Y = 0.1;               // px — drum-strip "settled" threshold
     var _TUNER_IN_TUNE_THRESHOLD = 2;
     var _TUNER_STRIP_START_MIDI = 14;  // ~18 Hz — covers 20 Hz minimum
     var _TUNER_STRIP_END_MIDI = 84;    // ~1047 Hz C6
@@ -321,9 +323,34 @@
             currentAngle += (targetAngle - currentAngle) * lf;
             _setNeedle(currentAngle);
 
+            // Stop once the needle has settled on its target — a static needle
+            // needs no repaint. update() re-kicks the loop when a new reading
+            // moves the target, so this idles the always-on tuner (no signal /
+            // steady pitch) instead of pinning a core at 60 fps forever.
+            if (Math.abs(targetDrumY - currentDrumY) <= _SETTLE_Y
+                    && Math.abs(targetAngle - currentAngle) <= _SETTLE_A) {
+                currentDrumY = targetDrumY; currentAngle = targetAngle;
+                freqStrip.style.transform = 'translateY(' + currentDrumY + 'px)';
+                noteStrip.style.transform = 'translateY(' + currentDrumY + 'px)';
+                _setNeedle(currentAngle);
+                rafId = null;
+                return;
+            }
             rafId = requestAnimationFrame(_animate);
         }
 
+        // Restart the loop only when there's actually something to animate toward
+        // (a new target). Reset lastTime so the first frame after an idle gap
+        // doesn't take one big easing step.
+        function _kick() {
+            if (rafId === null
+                    && (Math.abs(targetDrumY - currentDrumY) > _SETTLE_Y
+                        || Math.abs(targetAngle - currentAngle) > _SETTLE_A)) {
+                lastTime = performance.now();
+                rafId = requestAnimationFrame(_animate);
+            }
+        }
+
         rafId = requestAnimationFrame(_animate);
 
         // ── Public API ────────────────────────────────────────────────
@@ -360,6 +387,7 @@
                 bulbEl.style.backgroundColor = '#2a1010';
                 bulbEl.style.border = '2px solid #4a2020';
                 bulbEl.style.boxShadow = 'none';
+                _kick();   // animate back to rest, then the loop self-stops
                 return;
             }
 
@@ -376,6 +404,7 @@
                 bulbEl.style.border = '2px solid #4a2020';
                 bulbEl.style.boxShadow = 'none';
             }
+            _kick();   // a new reading moved the target → run until it settles
         }
 
         function destroy() {