feat(playground): EOC chain wired into audio graph, bypass mode manual sliders (meml-xp3)

- Wire EOCChain into audio graph after c15.start() (both start-btn and
  quick-play paths); guarded by _eocInited flag so init happens once per
  AudioContext lifetime
- getOutputNode() on C15Adapter now returns limiter (last node before
  destination) so EOC inserts correctly between limiter and destination
- Expose limiterNode getter on C15Bridge
- Add getCurrentParamValue(i) to EOCModule base class, backed by _paramValues
  array that setParam() writes to
- Add _buildParamSliders() to EOCChainUI: collapsible ▶ params toggle per
  module row, one range slider per paramMeta entry, calls module.setParam()
  on input; labelled "manual" when nispsMode=bypass
- eoc:change listener in a-app.js logs paramCount (hook point for future modes)
- saveState()/loadState() persist eocModules (id, enabled, params) and
  eocNispsMode; restore re-adds modules via moduleFactory and re-applies values
- CSS: eoc-params-section, eoc-params-toggle, eoc-param-row/label/slider;
  eoc-module-row gains flex-wrap to accommodate params section below controls

playground/js/eoc/eoc-module.js

@@ -33,6 +33,8 @@ export class EOCModule {
     this._bypassOut  = null;  // GainNode: output exit point
     this._bypassDry  = null;  // GainNode: direct input→output path when bypassed
     this._initialized = false;
+    // Stored normalized param values — set via setParam(), read by getCurrentParamValue()
+    this._paramValues = [];
   }
 
   // ---------------------------------------------------------------------------
@@ -184,7 +186,24 @@ export class EOCModule {
    * @param {number} normalizedValue — [0, 1]
    */
   setParam(index, normalizedValue) { // eslint-disable-line no-unused-vars
-    // default no-op — override in subclass
+    // Store the value so getCurrentParamValue() can read it back
+    this._paramValues[index] = normalizedValue;
+    // default no-op — override in subclass for actual audio effect
+  }
+
+  /**
+   * Get the last normalized value set for a parameter.
+   * Returns the param's init value (from paramMeta) if never explicitly set.
+   *
+   * @param {number} index — 0-based index into paramMeta
+   * @returns {number} normalized value [0, 1]
+   */
+  getCurrentParamValue(index) {
+    if (this._paramValues[index] !== undefined) {
+      return this._paramValues[index];
+    }
+    const meta = this.paramMeta[index];
+    return meta ? (meta.init ?? 0) : 0;
   }
 
   // ---------------------------------------------------------------------------

playground/js/synth/c15-adapter.js

@@ -144,13 +144,15 @@ export class C15Adapter extends SynthEngine {
   // --- Audio graph ---
 
   /**
-   * Return the master gain node. Connect this to a compressor or destination.
+   * Return the limiter node — the last AudioNode before destination.
-   * Only available after init() completes.
+   * This is the correct insertion point for post-processing (e.g. EOCChain).
+   * Falls back to masterGain before start() is called.
+   * Only useful after init() completes.
    *
-   * @returns {GainNode}
+   * @returns {AudioNode}
    */
   getOutputNode() {
-    return this._bridge.masterGain;
+    return this._bridge.limiterNode ?? this._bridge.masterGain;
   }
 
   // --- C15-specific passthrough (for MIDIInput and volume controls) ---

playground/js/synth/c15-bridge.js

@@ -80,6 +80,14 @@ export class C15Bridge {
   /** SharedArrayBuffer for the ring buffer — available after start() */
   get sharedBuffer() { return this._sab; }
 
+  /**
+   * The limiter node — the last AudioNode before destination.
+   * Use this as the input to any post-processing chain (e.g. EOCChain).
+   * Only available after start().
+   * @returns {DynamicsCompressorNode|null}
+   */
+  get limiterNode() { return this.limiter ?? null; }
+
   _status(msg) {
     console.log('[C15]', msg);
     this._onStatusChange?.(msg);

playground/js/ui/eoc-chain-ui.js

@@ -224,6 +224,12 @@ export const EOCChainUI = {
     });
     row.appendChild(removeBtn);
 
+    // --- Manual param sliders (shown in bypass mode, or when module has params) ---
+    if (mod.paramCount > 0) {
+      const paramsSection = this._buildParamSliders(mod);
+      row.appendChild(paramsSection);
+    }
+
     // --- HTML5 Drag-and-drop ---
     row.addEventListener('dragstart', (e) => {
       this._dragId = mod.id;
@@ -283,6 +289,59 @@ export const EOCChainUI = {
     return row;
   },
 
+  // Per-module param sliders (collapsible, shown only when paramCount > 0)
+  _buildParamSliders(mod) {
+    const section = document.createElement('div');
+    section.className = 'eoc-params-section';
+
+    // Toggle button (chevron + label)
+    const toggleBtn = document.createElement('button');
+    toggleBtn.className = 'eoc-params-toggle';
+    const isManual = this._chain.nispsMode === 'bypass';
+    toggleBtn.textContent = isManual ? '▶ params (manual)' : '▶ params';
+    toggleBtn.title = 'Expand to show parameter sliders';
+
+    const sliderList = document.createElement('div');
+    sliderList.className = 'eoc-params-list eoc-params-collapsed';
+
+    toggleBtn.addEventListener('click', () => {
+      const collapsed = sliderList.classList.toggle('eoc-params-collapsed');
+      toggleBtn.textContent = collapsed
+        ? (isManual ? '▶ params (manual)' : '▶ params')
+        : (isManual ? '▼ params (manual)' : '▼ params');
+    });
+
+    // One slider per param
+    mod.paramMeta.forEach((meta, i) => {
+      const row = document.createElement('div');
+      row.className = 'eoc-param-row';
+
+      const label = document.createElement('label');
+      label.className = 'eoc-param-label';
+      label.textContent = meta.name ?? meta.id ?? `Param ${i}`;
+
+      const slider = document.createElement('input');
+      slider.type  = 'range';
+      slider.min   = '0';
+      slider.max   = '1';
+      slider.step  = '0.001';
+      slider.value = String(mod.getCurrentParamValue(i));
+      slider.className = 'eoc-param-slider';
+
+      slider.addEventListener('input', () => {
+        mod.setParam(i, parseFloat(slider.value));
+      });
+
+      row.appendChild(label);
+      row.appendChild(slider);
+      sliderList.appendChild(row);
+    });
+
+    section.appendChild(toggleBtn);
+    section.appendChild(sliderList);
+    return section;
+  },
+
   // Add-module bar
   _buildAddBar() {
     const bar = document.createElement('div');