fix(platform): inject composer pseudo packages into resolver

composer-runtime-api, composer-plugin-api, and composer are Composer
pseudo packages that don't exist on Packagist. The resolver was trying
to fetch them remotely (HTTP 404) because PackageName::is_platform()
didn't recognize them and detect_platform() didn't inject them.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

2 files changed, 49 insertions, 8 deletions

diff --git a/crates/mozart-core/src/platform.rs b/crates/mozart-core/src/platform.rs
index c1f187f..cf141a4 100644
--- a/crates/mozart-core/src/platform.rs
+++ b/crates/mozart-core/src/platform.rs
@@ -31,6 +31,17 @@ pub fn is_platform_package(name: &str) -> bool {
 
 // ─── Detection ───────────────────────────────────────────────────────────────
 
+/// Composer runtime API version that Mozart emulates.
+/// Corresponds to `Composer::RUNTIME_API_VERSION` in Composer.
+pub const COMPOSER_RUNTIME_API_VERSION: &str = "2.2.2";
+
+/// Composer plugin API version that Mozart emulates.
+/// Corresponds to `PluginInterface::PLUGIN_API_VERSION` in Composer.
+pub const COMPOSER_PLUGIN_API_VERSION: &str = "2.6.0";
+
+/// Composer version that Mozart emulates.
+pub const COMPOSER_VERSION: &str = "2.8.0";
+
 /// Detect all platform packages by running a single PHP invocation.
 ///
 /// Returns an empty vec if PHP is not found or not executable.
@@ -168,8 +179,36 @@ pub fn parse_platform_info(output: &str) -> Vec<PlatformPackage> {
         }
 
         result.extend(packages);
+
+        // Add Composer pseudo packages
+        result.push(PlatformPackage {
+            name: "composer".to_string(),
+            version: COMPOSER_VERSION.to_string(),
+        });
+        result.push(PlatformPackage {
+            name: "composer-plugin-api".to_string(),
+            version: COMPOSER_PLUGIN_API_VERSION.to_string(),
+        });
+        result.push(PlatformPackage {
+            name: "composer-runtime-api".to_string(),
+            version: COMPOSER_RUNTIME_API_VERSION.to_string(),
+        });
+
         result
     } else {
+        // Even without PHP, provide Composer pseudo packages
+        packages.push(PlatformPackage {
+            name: "composer".to_string(),
+            version: COMPOSER_VERSION.to_string(),
+        });
+        packages.push(PlatformPackage {
+            name: "composer-plugin-api".to_string(),
+            version: COMPOSER_PLUGIN_API_VERSION.to_string(),
+        });
+        packages.push(PlatformPackage {
+            name: "composer-runtime-api".to_string(),
+            version: COMPOSER_RUNTIME_API_VERSION.to_string(),
+        });
         packages
     }
 }
@@ -290,6 +329,11 @@ mod tests {
 
         let ext_ctype = packages.iter().find(|p| p.name == "ext-ctype");
         assert!(ext_ctype.is_some());
+
+        // Composer pseudo packages should always be present
+        assert!(packages.iter().any(|p| p.name == "composer"));
+        assert!(packages.iter().any(|p| p.name == "composer-plugin-api"));
+        assert!(packages.iter().any(|p| p.name == "composer-runtime-api"));
     }
 
     #[test]
diff --git a/crates/mozart-registry/src/resolver.rs b/crates/mozart-registry/src/resolver.rs
index e3554be..66864f7 100644
--- a/crates/mozart-registry/src/resolver.rs
+++ b/crates/mozart-registry/src/resolver.rs
@@ -107,15 +107,9 @@ impl PackageName {
         PackageName(Self::ROOT.to_string())
     }
 
-    /// Returns true if this is a platform package (php, ext-*, lib-*).
+    /// Returns true if this is a platform package (php, ext-*, lib-*, composer pseudo packages).
     pub fn is_platform(&self) -> bool {
-        self.0 == "php"
-            || self.0.starts_with("ext-")
-            || self.0.starts_with("lib-")
-            || self.0 == "php-64bit"
-            || self.0 == "php-ipv6"
-            || self.0 == "php-zts"
-            || self.0 == "php-debug"
+        mozart_core::platform::is_platform_package(&self.0)
     }
 
     /// Returns true if this is the virtual root package.
@@ -711,6 +705,9 @@ mod tests {
         assert!(PackageName("php".to_string()).is_platform());
         assert!(PackageName("ext-json".to_string()).is_platform());
         assert!(PackageName("lib-curl".to_string()).is_platform());
+        assert!(PackageName("composer".to_string()).is_platform());
+        assert!(PackageName("composer-plugin-api".to_string()).is_platform());
+        assert!(PackageName("composer-runtime-api".to_string()).is_platform());
         assert!(!PackageName("monolog/monolog".to_string()).is_platform());
         assert!(!PackageName("vendor/package".to_string()).is_platform());
     }