feat(presets): seed default overdrive/delay/reverb/chorus presets

Add Bank 2 'FX Bench' with 4 dedicated factory presets:
- Overdrive Bench: noise_gate + overdrive + volume
- Delay Bench: noise_gate + eq + delay + volume
- Reverb Bench: noise_gate + eq + reverb + volume
- Chorus Bench: noise_gate + eq + chorus + volume

Each preset showcases a single core effect with well-tuned default
parameters derived from the pipeline DSP schemas.

All 46 existing tests pass.

presets/factory/bank_2/bank.json

@@ -0,0 +1,5 @@
+{
+  "number": 2,
+  "name": "FX Bench",
+  "preset_count": 4
+}