Extract schematic layout geometry into SchematicLayout and unit-test it

CLAUDE.md

@@ -400,6 +400,12 @@ appear as boxes/pins there).
   `root_response`/`root_loaded`.
 - **`PropertiesView`** — renders the current `PropertiesStore` contents as a
   two-column name/value table into the "Properties" bottom-panel tab.
+- **`SchematicLayout`** — the schematic's pure placement geometry, split out
+  of `EquipotentialView` so it's unit-testable without ImGui frames or a
+  provider (`tests/SchematicLayoutTest.cpp`): `IncrementalLayout` (per-net
+  instance placement and column de-overlap) and `layoutHierarchyGroups()`
+  (module frames). Changes to how the schematic is laid out belong here,
+  with a test; `EquipotentialView` only turns the result into drawn shapes.
 
 ### Diagnosis overlay
 

CMakeLists.txt

@@ -74,6 +74,7 @@ set(CORE_SOURCES
   src/GUIData.cpp
   src/NetlistTree.cpp
   src/EquipotentialView.cpp
+  src/SchematicLayout.cpp
   src/SchematicView.cpp
   src/DiagnosisStore.cpp
   src/DiagnosisView.cpp
@@ -206,7 +207,7 @@ endif()
 # Target 3: naja-schematic-tests — GUI-independent unit tests
 # ============================================================
 # Native only: exercises the logic layer (JSON parsing, DiagnosisStore,
-# SourceStore, NetlistTree structure) without SDL/OpenGL/naja. Links only
+# SourceStore, NetlistTree structure, SchematicLayout geometry) without SDL/OpenGL/naja. Links only
 # ImGui's core (imgui.cpp/imgui_draw.cpp/imgui_tables.cpp/imgui_widgets.cpp),
 # not the SDL2/OpenGL3 backends, since none of the tested code needs a real
 # render backend -- render()/draw calls are never invoked from tests.
@@ -233,6 +234,7 @@ if(NOT EMSCRIPTEN_BUILD)
       src/DiagnosisStore.cpp
       src/SourceStore.cpp
       src/PropertiesStore.cpp
+      src/SchematicLayout.cpp
       ${IMGUI_DIR}/imgui.cpp
       ${IMGUI_DIR}/imgui_draw.cpp
       ${IMGUI_DIR}/imgui_tables.cpp

REUSE.toml

@@ -67,6 +67,8 @@ path = [
   "src/PropertiesView.cpp",
   "src/PropertiesView.h",
   "src/RenderTypes.h",
+  "src/SchematicLayout.cpp",
+  "src/SchematicLayout.h",
   "src/SchematicView.cpp",
   "src/SchematicView.h",
   "src/SourceStore.cpp",
@@ -85,6 +87,7 @@ path = [
   "tests/DiagnosisStoreTest.cpp",
   "tests/FakeNetlistProvider.h",
   "tests/NetlistTreeTest.cpp",
+  "tests/SchematicLayoutTest.cpp",
   "tests/SourceStoreTest.cpp",
   "tests/TypesJsonTest.cpp",
 ]