chore: land janitor round 1 and graft integration

Round 1 findings and fixes, all previously uncommitted:
- FXProcessor per-slot DSP history repair (HEAD does not compile without it)
- SynthVoice::getModulationValue, editor control-lock guard
- ExactCompare.h naming the deliberate exact float comparisons
- KnobLookAndFeel replacing the never-installed SerumLookAndFeel
- 55 first-party compiler warnings to 0
- AGENT.md renamed to AGENTS.md across Source/
- graft repository context graph and its hooks
- JANITOR_TASKS.md and UI_UX_AUDIT.md records

Source/Params.cpp

@@ -24,6 +24,7 @@ juce::String modSourceName (ModSource s)
         case ModSource::Macro3:    return "Macro 3";
         case ModSource::Macro4:    return "Macro 4";
         case ModSource::Random:    return "Random";
+        case ModSource::Count:     return {};
         default:                   return {};
     }
 }
@@ -41,6 +42,7 @@ juce::String modSourceToString (ModSource s)
         case ModSource::Macro1: return "macro1"; case ModSource::Macro2: return "macro2";
         case ModSource::Macro3: return "macro3"; case ModSource::Macro4: return "macro4";
         case ModSource::Random: return "random";
+        case ModSource::Count: return {};
         default: return {};
     }
 }
@@ -88,6 +90,8 @@ juce::String modTargetName (ModTarget t)
         case ModTarget::Fx3Mix: return "FX 3 Mix"; case ModTarget::Fx4Mix: return "FX 4 Mix";
         case ModTarget::Fx5Mix: return "FX 5 Mix"; case ModTarget::Fx6Mix: return "FX 6 Mix";
         case ModTarget::Fx7Mix: return "FX 7 Mix"; case ModTarget::Fx8Mix: return "FX 8 Mix";
+        case ModTarget::None: return {};
+        case ModTarget::Count: return {};
         default: return {};
     }
 }
@@ -127,6 +131,8 @@ juce::String modTargetParamId (ModTarget t)
         case ModTarget::Fx3Mix: return ids::fx3Mix; case ModTarget::Fx4Mix: return ids::fx4Mix;
         case ModTarget::Fx5Mix: return ids::fx5Mix; case ModTarget::Fx6Mix: return ids::fx6Mix;
         case ModTarget::Fx7Mix: return ids::fx7Mix; case ModTarget::Fx8Mix: return ids::fx8Mix;
+        case ModTarget::None: return {};
+        case ModTarget::Count: return {};
         default: return {};
     }
 }