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/GUI/ToggleButton.cpp

@@ -33,21 +33,29 @@ void ToggleButton::paint (juce::Graphics& g)
     const float ledSize = juce::jmin (bounds.getHeight() - 16.0f, 16.0f);
     const juce::Rectangle<float> led ((bounds.getWidth() - ledSize) * 0.5f, 4.0f, ledSize, ledSize);
 
+    const bool live = isEnabled();
+    const bool hovered = live && isMouseOverOrDragging();
+
     if (state)
     {
-        g.setColour (onColour.withAlpha (0.35f));
+        // Hover brightens the halo, disabled dims it, so the three states are
+        // distinguishable without relying on colour alone.
+        const float halo = live ? (hovered ? 0.55f : 0.35f) : 0.15f;
+        g.setColour (onColour.withAlpha (halo));
         g.fillEllipse (led.expanded (6.0f));
-        g.setColour (onColour);
+        g.setColour (live ? onColour : onColour.withAlpha (0.4f));
     }
     else
     {
-        g.setColour (theme::outline);
+        g.setColour (hovered ? theme::textDim : theme::outline);
     }
     g.fillEllipse (led);
     g.setColour (state ? juce::Colours::black : theme::textDim);
-    g.drawEllipse (led, 1.0f);
+    g.drawEllipse (led, live ? (hovered ? 1.6f : 1.0f) : 0.8f);
 
-    g.setColour (state ? theme::text : theme::textDim);
+    const auto labelColour = ! live ? theme::outline
+                                    : (state ? theme::text : (hovered ? theme::text : theme::textDim));
+    g.setColour (labelColour);
     g.setFont (juce::Font (11.0f));
     g.drawText (label, 0, (int) (led.getBottom() + 2), getWidth(), 14, juce::Justification::centred, false);
 }