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 <noreply@anthropic.com>

build.rs

@@ -1,30 +1,11 @@
-// build.rs — auto-generates src/modules/registry.rs
+// build.rs — Windows executable icon embedding.
 //
-// Scans src/modules/ for subdirectories containing a mod.rs file.
-// Each subdirectory name like "home" maps to a struct "HomeModule"
-// defined in src/modules/home/mod.rs.
-//
-// Rules for a directory to be picked up:
-//   • Located directly in src/modules/
-//   • Contains a mod.rs file
-//   • Does NOT contain plugin.toml (add-ons register via BuiltinPlugin::ribbon)
-//   • Defines a pub struct {PascalCase}Module implementing CadModule
-//     (unit struct — no ::new() needed)
-//
-// Tab display order: the PRIORITY list below controls order.
-// Unlisted modules appear after priority modules, sorted alphabetically.
-//
-// Adding a new 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. cargo build  →  module appears in the ribbon
+// The core ribbon module registry used to be generated here; it is now a
+// hand-written static list in src/modules/registry.rs.
 
-use std::fs;
+#[cfg(windows)]
 use std::path::Path;
 
-// Display order for known modules; unknown modules follow alphabetically.
-const PRIORITY: &[&str] = &["draw", "model", "insert", "annotate", "view", "manage"];
-
 fn main() {
     // Windows: embed AppIcon.ico into the .exe so the executable carries its
     // own icon (Explorer, taskbar, Start-menu tile, file associations). The
@@ -41,70 +22,4 @@ fn main() {
             }
         }
     }
-
-    let mods_dir = Path::new("src/modules");
-    println!("cargo:rerun-if-changed=src/modules");
-
-    // Collect subdirectories that contain mod.rs.
-    let mut modules: Vec<String> = fs::read_dir(mods_dir)
-        .expect("src/modules/ not found")
-        .filter_map(|e| {
-            let entry = e.ok()?;
-            if !entry.file_type().ok()?.is_dir() {
-                return None;
-            }
-            let name = entry.file_name().into_string().ok()?;
-            let mod_file = mods_dir.join(&name).join("mod.rs");
-            let plugin_toml = mods_dir.join(&name).join("plugin.toml");
-            if mod_file.exists() && !plugin_toml.exists() {
-                Some(name)
-            } else {
-                None
-            }
-        })
-        .collect();
-
-    // Sort: priority order first, then alphabetical for the rest.
-    modules.sort_by_key(|name| {
-        let pri = PRIORITY.iter().position(|p| *p == name.as_str());
-        (pri.map(|i| i as u32).unwrap_or(u32::MAX), name.clone())
-    });
-
-    // snake_case → PascalCase + "Module"
-    let to_struct = |s: &str| -> String {
-        s.split('_')
-            .map(|w| {
-                let mut c = w.chars();
-                match c.next() {
-                    None => String::new(),
-                    Some(f) => f.to_uppercase().collect::<String>() + c.as_str(),
-                }
-            })
-            .collect::<String>()
-            + "Module"
-    };
-
-    let mut out = String::from(
-        "// AUTO-GENERATED by build.rs — do not edit by hand.\n\
-         // To add a module: create src/modules/my_name/mod.rs + add `pub mod my_name;` to modules/mod.rs.\n\n\
-         use crate::modules::CadModule;\n\n\
-         /// Returns one boxed instance of every registered CAD module.\n\
-         /// Called once at startup by `Ribbon::new()`.\n\
-         pub fn all_modules() -> Vec<Box<dyn CadModule>> {\n\
-         \tvec![\n",
-    );
-
-    for module in &modules {
-        let s = to_struct(module);
-        out.push_str(&format!("\t\tBox::new(super::{module}::{s}),\n"));
-    }
-
-    out.push_str("\t]\n}\n");
-
-    let out_dir = std::env::var("OUT_DIR").expect("OUT_DIR not set");
-    let out_path = Path::new(&out_dir).join("modules_registry.rs");
-    let current = fs::read_to_string(&out_path).unwrap_or_default();
-    if current != out {
-        fs::write(&out_path, &out).expect("failed to write modules_registry.rs");
-    }
 }