Merge selfhosting-dev into main (Core-13 pure CI/tests + LLVM bridge) (#126)

* WIP: sync before merging origin/main

* fix: unify using/module + build CLI; add missing helper in runner; build passes; core smokes green; jit any.len string now returns 3

* Apply local changes after merging main; keep docs/phase-15 removed per main; add phase-15.1 docs and tests

* Remove legacy docs/phase-15/README.md to align with main

* integration: add Core-13 pure CI, tests, and minimal LLVM execute bridge (no docs) (#125)

Co-authored-by: Tomoaki <tomoaki@example.com>

---------

Co-authored-by: Selfhosting Dev <selfhost@example.invalid>
Co-authored-by: Tomoaki <tomoaki@example.com>

src/runtime/mod.rs

@@ -22,6 +22,7 @@ pub mod type_registry; // Phase 12: TypeId→TypeBox 解決（雛形）
 pub mod host_handles; // C ABI(TLV) 向け HostHandle レジストリ（ユーザー/内蔵Box受け渡し）
 pub mod host_api; // C ABI: plugins -> host 逆呼び出しAPI（TLSでVMに橋渡し）
 pub mod extern_registry; // ExternCall (env.*) 登録・診断用レジストリ
+pub mod modules_registry; // env.modules minimal registry
 
 #[cfg(test)]
 mod tests;