[auto] require head visible at all times, reset to framing/paused if lost

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/gestureDetector.ts

@@ -194,6 +194,26 @@ export function detectGesture(
     return null
   }
 
+  // Require head visible at all times (except framing, which has its own check)
+  if (state.calibrationStatus !== 'framing') {
+    const nose = landmarks2D[0]
+    const noseVis = nose && (nose.visibility === undefined || nose.visibility >= 0.5)
+    if (!noseVis) {
+      if (state.calibrationStatus === 'calibrating') {
+        state.calibrationStatus = 'framing'
+        state.feetVisibleSince = null
+        state.baselineSamplesL = []
+        state.baselineSamplesR = []
+        log(`[gesture] lost head, reset to framing`)
+      } else if (state.calibrationStatus === 'ready') {
+        state.calibrationStatus = 'paused'
+        state.activeStep = null
+        log(`[gesture] lost head during play, paused`)
+      }
+      return null
+    }
+  }
+
   const emit = (signal: GestureSignal): GestureSignal => {
     state.activeSignal = signal
     state.signalShowUntil = now + SIGNAL_DISPLAY_MS