refactor(source): move every implementation into its module directory

- 36 files move into the module whose AGENTS.md already claimed them:
  Engine/, Synth/, Modulation/, Params/, Plugin/, GUI/, EffectUnits/, Resources/
- Source/engine, modulation, params, plugin and synth become Engine,
  Modulation, Params, Plugin and Synth, matching the directories that already
  hold code
- ExactCompare.h stays at the Source/ root as the one shared header
- SERUMALT_INCLUDE_DIRS adds one include directory per module, so the 31
  parent-relative includes become plain names with no path prefix
- the module AGENTS.md files list owned files instead of describing a move
  that had not happened, and README.md and AGENTS.md describe the real tree

Verified: the harness passes CTest, the Linux VST3 and Standalone link, the
Windows cross-build passes its module checks, each configure exposes only its
own targets, no first-party warning line appears, and the generated Windows
manifest is unchanged.

Source/EffectUnits/AGENTS.md

@@ -2,7 +2,7 @@
 
 ## Owned files
 
-- Related rack implementation: `../FXProcessor.h`, `../FXProcessor.cpp`
+- FXProcessor.h, FXProcessor.cpp
 - Biquad.h
 - Hyper.h, Hyper.cpp
 - Chorus.h, Chorus.cpp
@@ -27,7 +27,7 @@
 ## IF-THEN
 
 - IF a unit needs a delay line THEN allocate it in `prepare()` at the full required length and only read and write it in `process`.
-- Include the existing rack interface via `../FXProcessor.h`; no source relocation is implied by this guidance.
+- Include the rack interface via `FXProcessor.h`.
 
 ## Examples
 

Source/EffectUnits/Chorus.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include "../FXProcessor.h"
+#include "FXProcessor.h"
 
 namespace serum
 {

Source/EffectUnits/Compressor.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include "../FXProcessor.h"
+#include "FXProcessor.h"
 
 namespace serum
 {

Source/EffectUnits/Delay.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include "../FXProcessor.h"
+#include "FXProcessor.h"
 
 namespace serum
 {

Source/EffectUnits/Distortion.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include "../FXProcessor.h"
+#include "FXProcessor.h"
 #include "Biquad.h"
 
 namespace serum

Source/EffectUnits/EQ.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include "../FXProcessor.h"
+#include "FXProcessor.h"
 #include "Biquad.h"
 
 namespace serum

Source/EffectUnits/Flanger.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include "../FXProcessor.h"
+#include "FXProcessor.h"
 
 namespace serum
 {

Source/EffectUnits/Hyper.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include "../FXProcessor.h"
+#include "FXProcessor.h"
 #include "Biquad.h"
 
 namespace serum

Source/EffectUnits/Phaser.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include "../FXProcessor.h"
+#include "FXProcessor.h"
 
 namespace serum
 {

Source/EffectUnits/Reverb.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include "../FXProcessor.h"
+#include "FXProcessor.h"
 
 namespace serum
 {

Source/Engine/AGENTS.md

@@ -1,9 +1,8 @@
 # engine module
 
-## Related source files
+## Owned files
 
-This directory contains guidance; the implementation remains in `../Engine.h`
-and `../Engine.cpp`.
+- Engine.h, Engine.cpp
 
 ## Rules
 

Source/GUI/AGENTS.md

@@ -2,7 +2,7 @@
 
 ## Owned files
 
-- Related editor implementation: `../PluginEditor.h`, `../PluginEditor.cpp`
+- PluginEditor.h, PluginEditor.cpp
 - Knob.h, Knob.cpp
 - KnobLookAndFeel.h, KnobLookAndFeel.cpp
 - ToggleButton.h, ToggleButton.cpp

Source/GUI/Display.h

@@ -1,7 +1,7 @@
 #pragma once
 
 #include <JuceHeader.h>
-#include "../Resources.h"
+#include "Resources.h"
 
 namespace serum
 {

Source/GUI/EnvelopeDisplay.cpp

@@ -1,6 +1,6 @@
 #include "EnvelopeDisplay.h"
-#include "../Envelope.h"
-#include "../ExactCompare.h"
+#include "Envelope.h"
+#include "ExactCompare.h"
 
 namespace serum
 {

Source/GUI/EnvelopeDisplay.h

@@ -1,8 +1,8 @@
 #pragma once
 
 #include <JuceHeader.h>
-#include "../Resources.h"
-#include "../Params.h"
+#include "Resources.h"
+#include "Params.h"
 
 namespace serum
 {

Source/GUI/FilterDisplay.cpp

@@ -1,5 +1,5 @@
 #include "FilterDisplay.h"
-#include "../ExactCompare.h"
+#include "ExactCompare.h"
 
 namespace serum
 {

Source/GUI/FilterDisplay.h

@@ -1,8 +1,8 @@
 #pragma once
 
 #include <JuceHeader.h>
-#include "../Resources.h"
-#include "../Params.h"
+#include "Resources.h"
+#include "Params.h"
 
 namespace serum
 {

Source/GUI/Knob.h

@@ -2,7 +2,7 @@
 
 #include <JuceHeader.h>
 #include <memory>
-#include "../Resources.h"
+#include "Resources.h"
 #include "KnobLookAndFeel.h"
 
 namespace serum

Source/GUI/KnobLookAndFeel.h

@@ -1,7 +1,7 @@
 #pragma once
 
 #include <JuceHeader.h>
-#include "../Resources.h"
+#include "Resources.h"
 
 namespace serum
 {

Source/GUI/LFODisplay.cpp

@@ -1,5 +1,5 @@
 #include "LFODisplay.h"
-#include "../ExactCompare.h"
+#include "ExactCompare.h"
 
 namespace serum
 {

Source/GUI/LFODisplay.h

@@ -1,9 +1,9 @@
 #pragma once
 
 #include <JuceHeader.h>
-#include "../Resources.h"
-#include "../Params.h"
-#include "../LFO.h"
+#include "Resources.h"
+#include "Params.h"
+#include "LFO.h"
 
 namespace serum
 {

Source/GUI/Panel.h

@@ -1,7 +1,7 @@
 #pragma once
 
 #include <JuceHeader.h>
-#include "../Resources.h"
+#include "Resources.h"
 
 namespace serum
 {

Source/GUI/ToggleButton.h

@@ -1,7 +1,7 @@
 #pragma once
 
 #include <JuceHeader.h>
-#include "../Resources.h"
+#include "Resources.h"
 
 namespace serum
 {

Source/GUI/WaveformDisplay.h

@@ -1,9 +1,9 @@
 #pragma once
 
 #include <JuceHeader.h>
-#include "../ExactCompare.h"
-#include "../Resources.h"
-#include "../Wavetable.h"
+#include "ExactCompare.h"
+#include "Resources.h"
+#include "Wavetable.h"
 
 namespace serum
 {

Source/Modulation/AGENTS.md

@@ -1,13 +1,10 @@
 # modulation module
 
-## Related source files
+## Owned files
 
-This directory contains guidance; implementations remain in the parent `Source/`
-directory:
-
-- `../ModulationMatrix.h`, `../ModulationMatrix.cpp`
-- `../MacroControls.h`, `../MacroControls.cpp`
-- `../RAVEButton.h`, `../RAVEButton.cpp`, which define `RaveController`
+- ModulationMatrix.h, ModulationMatrix.cpp
+- MacroControls.h, MacroControls.cpp
+- RAVEButton.h, RAVEButton.cpp, which define `RaveController`
 
 ## Rules
 

Source/Params/AGENTS.md

@@ -1,15 +1,14 @@
 # params module
 
-## Related source files
+## Owned files
 
-This directory contains guidance; the implementation remains in `../Params.h`
-and `../Params.cpp`.
+- Params.h, Params.cpp
 
 ## Rules
 
 - Use the `ids::` namespace for every APVTS parameter ID string.
 - Require one `ids::` entry per audio parameter, and one entry only.
-- Reach indexed parameters through the `paramIds::` arrays in `../Params.h`, which pair each
+- Reach indexed parameters through the `paramIds::` arrays in `Params.h`, which pair each
   ID with its slot: `paramIds::oscillators`, `paramIds::envAttack`, `paramIds::lfoRate`,
   `paramIds::fxType`, `paramIds::macros` and their siblings. Use a single `ids::` entry only
   when the parameter has no index.

Source/Plugin/AGENTS.md

@@ -1,9 +1,8 @@
 # plugin module
 
-## Related source files
+## Owned files
 
-This directory contains guidance; the implementation remains in
-`../PluginProcessor.h` and `../PluginProcessor.cpp`.
+- PluginProcessor.h, PluginProcessor.cpp
 
 ## Rules
 

Source/Presets/FactoryPresets.h

@@ -1,8 +1,8 @@
 #pragma once
 
 #include <JuceHeader.h>
-#include "../Params.h"
-#include "../ModulationMatrix.h"
+#include "Params.h"
+#include "ModulationMatrix.h"
 
 namespace serum
 {

Source/Resources/AGENTS.md

@@ -2,7 +2,7 @@
 
 ## Owned files
 
-- Related embedded assets and helpers: `../Resources.h`, `../Resources.cpp`
+- Resources.h, Resources.cpp
 - logo.svg
 - background.svg
 

Source/Synth/AGENTS.md

@@ -1,9 +1,6 @@
 # synth module
 
-## Related source files
-
-This directory contains guidance. All files listed below remain in the parent
-`Source/` directory.
+## Owned files
 
 - Wavetable.h, Wavetable.cpp
 - Oscillator.h, Oscillator.cpp

Source/Tests/TestMain.cpp

@@ -1,7 +1,7 @@
 #include <JuceHeader.h>
 #include <cmath>
 #include <iostream>
-#include "../PluginProcessor.h"
+#include "PluginProcessor.h"
 
 // ===========================================================================
 // Headless QA harness: instantiates the processor, plays notes through every