refactor(composer): unify Composer/PartialComposer via Rc handles

Model PHP's `Composer extends PartialComposer` as a PartialOrFullComposer
enum and merge partial_composer.rs into composer.rs. Introduce
ComposerHandle / PartialComposerHandle (plus their Weak variants) so the
graph can be shared, and build it at once with Rc::new_cyclic in the
factory to resolve the back-reference cycles.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/crates/shirabe/src/repository/platform_repository.rs b/crates/shirabe/src/repository/platform_repository.rs
index 17fde5d..8494e25 100644
--- a/crates/shirabe/src/repository/platform_repository.rs
+++ b/crates/shirabe/src/repository/platform_repository.rs
@@ -13,7 +13,8 @@ use shirabe_php_shim::{
 };
 use shirabe_semver::constraint::Constraint;
 
-use crate::composer::Composer;
+use crate::composer;
+use crate::composer::ComposerHandle;
 use crate::package::CompletePackage;
 use crate::package::CompletePackageInterface;
 use crate::package::Link;
@@ -153,7 +154,7 @@ impl PlatformRepository {
             }
         }
 
-        let mut pretty_version = Composer::get_version();
+        let mut pretty_version = composer::get_version();
         let mut version = self
             .version_parser
             .as_ref()
@@ -181,7 +182,7 @@ impl PlatformRepository {
         composer_plugin_api.set_description("The Composer Plugin API".to_string());
         self.add_package(Box::new(composer_plugin_api))?;
 
-        pretty_version = Composer::RUNTIME_API_VERSION.to_string();
+        pretty_version = composer::RUNTIME_API_VERSION.to_string();
         version = self
             .version_parser
             .as_ref()