feat(drum_highway_3d): hit FX — sparks, timing colors, lane flashes, kick pulse, open hi-hat (D2) (#697)

- Pooled spark bursts (PORTED highway_3d, pool 160) at the struck lane,
  timing-colored via _timingHex/_classifyTiming (±50ms window, inner 40%
  = on-time); streak-scaled counts (streakFx)
- Lane flashes resurrected as pooled additive gauss-tex quads at the hit
  line (timing-colored; red for wrong hits); kick = full-width quad
- Kick pulse: camera dip + amber floor wash, exp decay, hitFx-scaled
- Approach highlight: lane stripes brighten toward their next note
- Open hi-hat: hh_open renders a warm ring around the gem (closes TODO);
  orthogonal to accent/ghost/flam variants
- Settings: Hit sparks / Timing colours / Streak feedback toggles +
  Hit feedback intensity slider (drum_h3d_bg_*, live-applying)
- All FX resources pooled/shared, disposed in BOTH teardown paths
- Tests: _classifyTiming boundaries + FX defaults (10 total)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

plugins/drum_highway_3d/settings.html

@@ -54,6 +54,46 @@
             Soft light-bleed around the hit line and bright notes. Applies
             live; turn off to reclaim GPU headroom on weak machines.
         </p>
+
+        <label for="drumh3d-fx-sparks" class="flex items-center gap-2 text-xs text-gray-300 cursor-pointer mt-3">
+            <input type="checkbox" id="drumh3d-fx-sparks" checked
+                onchange="window.drumH3dSetFx && window.drumH3dSetFx('sparks', this.checked)">
+            Hit sparks
+        </label>
+        <p class="text-xs text-gray-500 mt-1">
+            A small particle burst on every scored pad hit.
+        </p>
+
+        <label for="drumh3d-fx-timing" class="flex items-center gap-2 text-xs text-gray-300 cursor-pointer mt-3">
+            <input type="checkbox" id="drumh3d-fx-timing" checked
+                onchange="window.drumH3dSetFx && window.drumH3dSetFx('timingFx', this.checked)">
+            Timing colours
+        </label>
+        <p class="text-xs text-gray-500 mt-1">
+            Tint hit feedback by timing — on-time green, early cyan, late
+            amber. Off = always green.
+        </p>
+
+        <label for="drumh3d-fx-streak" class="flex items-center gap-2 text-xs text-gray-300 cursor-pointer mt-3">
+            <input type="checkbox" id="drumh3d-fx-streak" checked
+                onchange="window.drumH3dSetFx && window.drumH3dSetFx('streakFx', this.checked)">
+            Streak feedback
+        </label>
+        <p class="text-xs text-gray-500 mt-1">
+            Spark bursts grow with your combo.
+        </p>
+
+        <label for="drumh3d-fx-hitfx" class="text-xs font-medium text-gray-400 mb-1 mt-3 block">
+            Hit feedback intensity <span id="drumh3d-fx-hitfx-val" class="text-gray-500 font-mono">0.70</span>
+        </label>
+        <input type="range" id="drumh3d-fx-hitfx"
+            min="0" max="1" step="0.05" value="0.7"
+            oninput="window.drumH3dSetFx && window.drumH3dSetFx('hitFx', this.value); document.getElementById('drumh3d-fx-hitfx-val').textContent = parseFloat(this.value).toFixed(2)"
+            class="w-full">
+        <p class="text-xs text-gray-500 mt-1">
+            Drives the lane flashes, approach glow and the kick camera pulse.
+            0 turns them off.
+        </p>
     </div>
 
     <!-- MIDI input -->
@@ -440,11 +480,20 @@
             // FX toggles (drum_h3d_bg_* — guitar-parity graphics controls).
             // Only explicit values override; absent/corrupt keys keep the
             // default (ON), matching screen.js readFxSettings.
-            const storedBloom = localStorage.getItem('drum_h3d_bg_bloom');
-            if (storedBloom === '1' || storedBloom === 'true') {
-                document.getElementById('drumh3d-fx-bloom').checked = true;
-            } else if (storedBloom === '0' || storedBloom === 'false') {
-                document.getElementById('drumh3d-fx-bloom').checked = false;
+            const hydrateFxBool = (key, elId) => {
+                const raw = localStorage.getItem('drum_h3d_bg_' + key);
+                if (raw === '1' || raw === 'true') document.getElementById(elId).checked = true;
+                else if (raw === '0' || raw === 'false') document.getElementById(elId).checked = false;
+            };
+            hydrateFxBool('bloom', 'drumh3d-fx-bloom');
+            hydrateFxBool('sparks', 'drumh3d-fx-sparks');
+            hydrateFxBool('timingFx', 'drumh3d-fx-timing');
+            hydrateFxBool('streakFx', 'drumh3d-fx-streak');
+            const storedHitFx = parseFloat(localStorage.getItem('drum_h3d_bg_hitFx'));
+            if (Number.isFinite(storedHitFx)) {
+                const v = Math.min(1, Math.max(0, storedHitFx));
+                document.getElementById('drumh3d-fx-hitfx').value = String(v);
+                document.getElementById('drumh3d-fx-hitfx-val').textContent = v.toFixed(2);
             }
         } catch (e) {
             console.warn('[Drum-Hwy3D settings] hydration failed:', e);