R1: Dashboard 500 fix, Phase 2/7 uncommitted changes

- Fix dashboard 500 when deps disconnected — _gather_state() now returns
  full defaults instead of bare {'connected': False}
- Phase 2: FX param schemas aligned with DSP implementations
- Phase 7: Pipeline routing, preset manager improvements
- Factory presets: cleanup and normalization

Fixes dashboard crash on disconnected state (dogfood issue #1)

src/dsp/pipeline.py

@@ -312,6 +312,13 @@ class AudioPipeline:
         # Cached filter coefficients per block
         self._coeffs: dict[str, tuple] = {}
 
+        # VU meter level tracking — updated on every process() call
+        # Smoothed RMS levels (0.0–1.0) read by web server for live VU meters
+        self._input_level: float = 0.0
+        self._output_level: float = 0.0
+        # Smoothing factor: ~50ms time constant at 48kHz/256 block
+        self._vu_alpha: float = np.exp(-BLOCK_SIZE / (0.05 * SAMPLE_RATE))
+
         logger.info("Audio pipeline initialized (block=%d, sr=%d)",
                      BLOCK_SIZE, SAMPLE_RATE)
 
@@ -373,12 +380,28 @@ class AudioPipeline:
 
     def _process_mono(self, audio_in: np.ndarray) -> np.ndarray:
         """Process a mono block through the full chain (all blocks)."""
+        # Update input VU level (RMS with envelope smoothing)
+        in_rms = np.sqrt(np.mean(audio_in ** 2) + _EPS)
+        self._input_level = (
+            self._input_level * self._vu_alpha
+            + in_rms * (1.0 - self._vu_alpha)
+        )
+
         buf = audio_in.copy()
         for idx, entry in enumerate(self._chain):
             if entry["bypass"] or not entry["enabled"]:
                 continue
             buf = self._process_single_block(buf, idx, entry)
-        return buf * self._master_volume
+        out = buf * self._master_volume
+
+        # Update output VU level
+        out_rms = np.sqrt(np.mean(out ** 2) + _EPS)
+        self._output_level = (
+            self._output_level * self._vu_alpha
+            + out_rms * (1.0 - self._vu_alpha)
+        )
+
+        return out
 
     def _process_4cm(self, audio_in: np.ndarray) -> np.ndarray:
         """Process stereo block with 4CM split routing.
@@ -397,6 +420,14 @@ class AudioPipeline:
         """
         ch0 = audio_in[0, :].copy()
         ch1 = audio_in[1, :].copy()
+
+        # Update input VU level from the guitar input channel (ch0)
+        in_rms = np.sqrt(np.mean(ch0 ** 2) + _EPS)
+        self._input_level = (
+            self._input_level * self._vu_alpha
+            + in_rms * (1.0 - self._vu_alpha)
+        )
+
         bp = self._routing_breakpoint
 
         for idx, entry in enumerate(self._chain):
@@ -413,6 +444,14 @@ class AudioPipeline:
         out = np.zeros_like(audio_in)
         out[0, :] = ch0 * self._master_volume
         out[1, :] = ch1 * self._master_volume
+
+        # Update output VU level from the processed effect return (ch1)
+        out_rms = np.sqrt(np.mean(out ** 2) + _EPS)
+        self._output_level = (
+            self._output_level * self._vu_alpha
+            + out_rms * (1.0 - self._vu_alpha)
+        )
+
         return out
 
     def _process_single_block(self, buf: np.ndarray, idx: int,