Surface control audit telemetry

docs/API.md

@@ -15,6 +15,8 @@ Health check.
 {"ok": true}
 ```
 
+`controlAudit` mirrors the control plane's HTTP reject counters (405/415/413/400) so runtime telemetry can spot abusive clients and the UI can keep ops aware of guardrail hits.
+
 `engine.state` spiegelt jetzt die Runtime-State-Maschine wider (idle, arming, prebuffering, running, degraded, muted, faulted, stopping) und bietet eine erste beobachtbare Basis für Fault-Transitions.
 
 
@@ -98,6 +100,12 @@ Live engine and driver telemetry. Only populated when TX is active.
     "underrunStreak": 0,
     "maxUnderrunStreak": 0,
     "effectiveSampleRateHz": 2280000
+  },
+  "controlAudit": {
+    "methodNotAllowed": 0,
+    "unsupportedMediaType": 0,
+    "bodyTooLarge": 0,
+    "unexpectedBody": 0
   }
 }
 ```

internal/control/ui.html

@@ -1193,6 +1193,19 @@ input.input-error {
         </div>
       </div>
 
+
+        <div class="sidebar-section">
+          <div class="sidebar-title">Control Audit</div>
+          <div class="section-note">Counts of 4xx rejects recorded by the control plane APIs.</div>
+          <div class="kv">
+            <div class="k">Rejects total</div><div class="v" id="audit-total">--</div>
+            <div class="k">405 Method Not Allowed</div><div class="v" id="audit-methodNotAllowed">--</div>
+            <div class="k">415 Unsupported Media Type</div><div class="v" id="audit-unsupportedMediaType">--</div>
+            <div class="k">413 Request Too Large</div><div class="v" id="audit-bodyTooLarge">--</div>
+            <div class="k">400 Unexpected Body</div><div class="v" id="audit-unexpectedBody">--</div>
+          </div>
+        </div>
+
       <div class="card panel" data-panel-key="shortcuts">
         <div class="panel-head" data-panel>
           <h2>Shortcuts</h2>
@@ -1974,6 +1987,7 @@ function render() {
   updateText('info-live', engine.state ? `${String(engine.state).toUpperCase()} / ${state.server.runtimeOk ? 'runtime ok' : 'runtime pending'}` : (state.server.configOk ? 'config only' : '--'));
 
   updateHealth(engine, driver, audioStream);
+  updateControlAudit(runtime.controlAudit);
   updateFaultHistory(engine);
   updateTransitionHistory();
   updateResetHint(engine);
@@ -2248,6 +2262,40 @@ function updateHealth(engine, driver, audioStream) {
 }
 
 
+
+function updateControlAudit(audit) {
+  const entries = [
+    { key: 'methodNotAllowed', id: 'audit-methodNotAllowed' },
+    { key: 'unsupportedMediaType', id: 'audit-unsupportedMediaType' },
+    { key: 'bodyTooLarge', id: 'audit-bodyTooLarge' },
+    { key: 'unexpectedBody', id: 'audit-unexpectedBody' },
+  ];
+  let total = 0;
+  let hasData = false;
+  entries.forEach(({ key, id }) => {
+    const raw = audit && typeof audit[key] !== 'undefined' ? Number(audit[key]) : NaN;
+    const value = Number.isFinite(raw) ? raw : null;
+    if (value != null) {
+      hasData = true;
+      total += value;
+    }
+    setAuditValue(id, value);
+  });
+  setAuditValue('audit-total', hasData ? total : null);
+}
+
+function setAuditValue(id, count) {
+  const el = $(id);
+  if (!el) return;
+  if (count == null) {
+    el.textContent = '--';
+    el.className = 'val';
+    return;
+  }
+  el.textContent = String(count);
+  el.className = 'val ' + (count > 0 ? 'warn' : 'good');
+}
+
 function updateFaultHistory(engine) {
   const container = $('fault-history');
   if (!container) return;