Attempt to add jerk correction

web/index.html

@@ -25,6 +25,7 @@
       <div class="batt-cells" id="battCells"></div>
       <span id="battPct">--%</span>
     </div>
+    <button class="btn btn-debug" id="debugBtn" onclick="openDebugModal()" style="display:none" title="IMU Debug Recorder"><span>DBG</span></button>
     <button class="btn btn-theme" id="themeBtn" onclick="cycleTheme()"><span>AUTO</span></button>
     <div class="status-pill" id="statusPill"><div class="dot"></div><span id="statusText">DISCONNECTED</span></div>
     <button class="btn btn-connect"    id="connectBtn"    onclick="doConnect()"><span>Connect</span></button>
@@ -100,6 +101,12 @@
 
     <div class="section-label">Tap Configuration</div>
     <div class="card">
+      <div class="param">
+        <div><div class="param-label">Tap Freeze Sensitivity</div><div class="param-desc">Jerk² threshold — lower = more aggressive cursor freeze during taps</div></div>
+        <input type="range" id="slJerkThreshold" min="500" max="10000" step="100" value="2000"
+          oninput="updateDisplay('jerkThreshold',this.value)" onchange="writeConfigBlob()">
+        <div class="param-value" id="valJerkThreshold">2000</div>
+      </div>
       <div class="param">
         <div><div class="param-label">Tap Threshold</div><div class="param-desc">Impact force needed · 1 LSB ≈ 62.5 mg at ±2g</div></div>
         <input type="range" id="slTapThreshold" min="1" max="31" step="1" value="12"
@@ -223,6 +230,32 @@
   </div>
 </div>
 
+<div class="overlay" id="debugOverlay">
+  <div class="modal debug-modal">
+    <div class="debug-header">
+      <h3>IMU Debug Recorder</h3>
+      <div style="display:flex;align-items:center;gap:8px">
+        <span class="debug-shock-badge" id="debugShockBadge">SHOCK</span>
+        <button class="debug-close" onclick="closeDebugModal()">✕</button>
+      </div>
+    </div>
+    <div class="debug-live" id="debugLive">
+      <table class="debug-table">
+        <thead><tr>
+          <th>ms</th><th>gX</th><th>gZ</th><th>aX</th><th>aY</th><th>aZ</th><th>mX</th><th>mY</th><th>flags</th>
+        </tr></thead>
+        <tbody id="debugRows"></tbody>
+      </table>
+    </div>
+    <div class="debug-controls">
+      <button class="debug-rec-btn" id="debugRecBtn" onclick="toggleDebugRec()">● REC</button>
+      <span class="debug-rec-count" id="debugRecCount">0 samples</span>
+      <button class="debug-ctrl-btn" onclick="saveDebugCSV()">Save CSV</button>
+      <button class="debug-ctrl-btn" onclick="clearDebugRec()">Clear</button>
+    </div>
+  </div>
+</div>
+
 <script src="app.js"></script>
 </body>
 </html>