refactor: replace build.rs module codegen with a static registry

The core ribbon registry no longer needs build-time generation. Replace
the generated all_modules() (included from OUT_DIR) with a hand-written
static list in src/modules/registry.rs, listing the seven built-in tabs
in display order.

Trim build.rs down to its only remaining job: embedding the Windows
executable icon via winresource (issue #107). The external plugin system
is unaffected — plugin::registry still appends dynamically-loaded add-on
tabs on top of the core list.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/modules/mod.rs

@@ -4,7 +4,7 @@
 //   1. Create `src/modules/my_name/` directory (no `plugin.toml`)
 //   2. Add `src/modules/my_name/mod.rs` implementing `CadModule` as `MyNameModule`
 //   3. Add `pub mod my_name;` below
-//   4. `cargo build` — tab appears via build.rs registry
+//   4. Add a `Box::new(my_name::MyNameModule)` line in `registry::all_modules()`
 //
 // To add an **add-on plugin** (Storm Sewer, …):
 //   See `docs/plugin-architecture.md` and copy `docs/plugin-template/`.
@@ -32,6 +32,6 @@ pub mod layout;
 pub mod manage;
 pub mod view;
 
-// ── Auto-generated module registry ───────────────────────────────────────
-// build.rs writes this file; it contains only `all_modules()`.
+// ── Core module registry ─────────────────────────────────────────────────
+// Hand-written `all_modules()` listing the built-in ribbon tabs.
 pub mod registry;

src/modules/registry.rs

@@ -1,4 +1,24 @@
-// AUTO-GENERATED include — see build.rs for the actual generator.
-// The generated registry is written to Cargo's OUT_DIR and included here so
-// the source tree is not modified during build.
-include!(concat!(env!("OUT_DIR"), "/modules_registry.rs"));
+// Core ribbon module registry — one boxed instance of every built-in CAD
+// module, in ribbon-tab display order. External add-ons are appended on top
+// of this list at runtime by `plugin::registry`.
+//
+// To add a core module:
+//   1. Create src/modules/my_name/mod.rs  (implement CadModule as MyNameModule)
+//   2. Add `pub mod my_name;` to src/modules/mod.rs
+//   3. Add one `Box::new(super::my_name::MyNameModule)` line below, in the
+//      position you want its tab to appear.
+use crate::modules::CadModule;
+
+/// Returns one boxed instance of every registered core CAD module.
+/// Called once at startup by `Ribbon::new()`.
+pub fn all_modules() -> Vec<Box<dyn CadModule>> {
+    vec![
+        Box::new(super::draw::DrawModule),
+        Box::new(super::model::ModelModule),
+        Box::new(super::insert::InsertModule),
+        Box::new(super::annotate::AnnotateModule),
+        Box::new(super::view::ViewModule),
+        Box::new(super::manage::ManageModule),
+        Box::new(super::layout::LayoutModule),
+    ]
+}