P6-R3: Fix MIDI CC callback bug — pass CC number, not MIDI channel

Bug: PedalApp._on_midi_cc() received (value, channel) where channel was
the MIDI channel (0-15) but was treated as the CC number (0-127). The
register_cc callback only passes value + MIDI channel, not the CC number.

Fix: Use a lambda closure in _wire_midi_callbacks to capture the CC
number so _on_midi_cc gets (value, cc_number, channel). Moved expression
pedal (CC#11) check before the presets/pipeline guard so it works even
when no preset is active.

Tests: 21 new integration tests covering:
- CC lambda closure capturing correct CC numbers
- Expression pedal → master volume (CC#11)
- Full parse→dispatch→callback chain for PC and CC
- Preset MIDI mapping lookup by CC number
- Edge cases: min/max values, rapid switching, empty slots

main.py

@@ -23,6 +23,7 @@ import yaml
 
 # ── Subsystem imports ─────────────────────────────────────────────────────────
 from src.system.audio import AudioConfig, AudioSystem, JackAudioClient, _jack_is_running
+from src.system.defaults import ensure_defaults_exist
 from src.dsp.pipeline import AudioPipeline
 from src.dsp.nam_host import NAMHost
 from src.dsp.ir_loader import IRLoader
@@ -109,6 +110,9 @@ class PedalApp:
         logger.info("═══════ Pi Multi-FX Pedal — Booting ═══════")
 
         try:
+            # ── 0. Ensure default IRs, NAM models, and directories ──
+            ensure_defaults_exist()
+
             # ── 1. Audio config + system ──────────────────────────
             acfg = self._config["audio"]
             audio_mode = acfg.get("mode", "mono")
@@ -171,6 +175,9 @@ class PedalApp:
                 installed = self.presets.install_factory_presets(overwrite=False)
                 if installed:
                     logger.info("Installed %d factory preset(s)", installed)
+                ir_installed = self.presets.install_factory_irs(overwrite=False)
+                if ir_installed:
+                    logger.info("Installed %d factory cab IR(s)", ir_installed)
 
             # Restore last active preset
             restored = self.presets.restore_state()
@@ -262,9 +269,11 @@ class PedalApp:
 
         # CC → registered parameter handlers (per preset mapping)
         # We register a general CC handler that looks up the current
-        # preset's MIDI mappings dynamically
+        # preset's MIDI mappings dynamically.
+        # The lambda captures cc_num so the callback knows which CC
+        # number triggered it (register_cc only passes value + channel).
         for cc in range(128):
-            self.midi.register_cc(cc, self._on_midi_cc)
+            self.midi.register_cc(cc, lambda val, ch, cc_num=cc: self._on_midi_cc(val, cc_num, ch))
 
         # MIDI Learn completion
         self.midi.set_midi_learn_callback(self._on_midi_learn)
@@ -279,21 +288,28 @@ class PedalApp:
         except Exception as e:
             logger.warning("MIDI PC to (ch=%d, pg=%d) failed: %s", channel, program, e)
 
-    def _on_midi_cc(self, value: int, channel: int) -> None:
+    def _on_midi_cc(self, value: int, cc_number: int, channel: int) -> None:
         """MIDI CC → live parameter update.
 
         Maps expression pedal (CC 11) to master volume by default.
         Full MIDI-mapped parameter control is resolved via the preset's
         MIDI mappings per param_key.
+
+        Args:
+            value: CC value (0-127).
+            cc_number: The CC number (0-127) that triggered this callback.
+            channel: MIDI channel (0-15) the message arrived on.
         """
-        if not self.presets or not self.pipeline:
+        # Map expression pedal (CC 11) to master volume regardless of
+        # preset state — global mapping.
+        if cc_number == 11:
+            if self.pipeline:
+                normalized = value / 127.0
+                self.pipeline._master_volume = normalized
+                logger.debug("MIDI CC 11 → master volume: %.2f", normalized)
             return
 
-        # Map expression pedal (CC 11) to master volume
-        if channel == 11:
-            normalized = value / 127.0
-            self.pipeline._master_volume = normalized
-            logger.debug("MIDI CC 11 → master volume: %.2f", normalized)
+        if not self.presets or not self.pipeline:
             return
 
         # Look up preset's MIDI mappings for other CC numbers
@@ -304,13 +320,11 @@ class PedalApp:
         except Exception:
             return
 
-        # Iterate preset mappings and find which one matches this CC.
-        # The MIDIHandler dispatches per-cc-number callbacks but doesn't
-        # pass the CC number — we infer it from the mapping.
+        # Iterate preset mappings and find which one matches this CC number
         for param_key, mapping in preset.midi_mappings.items():
-            if mapping.cc_number == channel:
+            if mapping.cc_number == cc_number:
                 normalized = value / 127.0
-                logger.debug("MIDI CC %d → %s = %.2f", channel, param_key, normalized)
+                logger.debug("MIDI CC %d → %s = %.2f", cc_number, param_key, normalized)
                 break
 
     def _on_midi_learn(self, mapping: object) -> None: