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/Oscillator.cpp

@@ -1,4 +1,5 @@
 #include "Oscillator.h"
+#include "ExactCompare.h"
 
 namespace serum
 {
@@ -12,9 +13,8 @@ void Oscillator::reset()
     paramsValid = false;
 }
 
-void Oscillator::noteOn (double freqHz, const OscParams& p, juce::uint32 seed)
+void Oscillator::noteOn (const OscParams& p, juce::uint32 seed)
 {
-    jassert (freqHz > 0.0);
     rng.setSeed (seed);
     initializedUnison = 0;
     paramsValid = false;
@@ -25,8 +25,9 @@ void Oscillator::setParams (const OscParams& p) noexcept
 {
     const int uni = juce::jlimit (1, kMaxUnison, p.unison);
     const bool countChanged = ! paramsValid || uni != activeUnison;
-    const bool detuneChanged = countChanged || p.detune != cachedParams.detune;
-    const bool panChanged = countChanged || p.pan != cachedParams.pan || p.spread != cachedParams.spread;
+    const bool detuneChanged = countChanged || changed (p.detune, cachedParams.detune);
+    const bool panChanged = countChanged || changed (p.pan, cachedParams.pan)
+                                          || changed (p.spread, cachedParams.spread);
     if (! detuneChanged && ! panChanged)
         return;
 
@@ -98,6 +99,7 @@ float Oscillator::warpPhase (float phase, const OscParams& p) const noexcept
         }
         case WarpMode::PWM: return phase;
         case WarpMode::Fold: return phase;
+        case WarpMode::Count: return phase;
         default: return phase;
     }
 }
@@ -114,6 +116,13 @@ float Oscillator::warpSample (float sample, const OscParams& p) const noexcept
         }
         case WarpMode::Fold:
             return std::sin (sample * (1.0f + amt * 5.0f) * 1.5707963267948966f);
+        case WarpMode::None:
+        case WarpMode::BendPlus:
+        case WarpMode::BendMinus:
+        case WarpMode::Sync:
+        case WarpMode::Asym:
+        case WarpMode::Mirror:
+        case WarpMode::Count:
         default:
             return sample;
     }