feat(installer): wire InstallerInterface marker-trait downcasts

Add as_binary_presence_interface and as_plugin_installer_mut to
InstallerInterface following the downloader marker-trait downcast
pattern, so InstallationManager can model the PHP instanceof checks in
ensureBinariesPresence and disablePlugins. Make BinaryPresenceInterface
take &mut self, resolving LibraryInstaller's stubbed trait impl.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/crates/shirabe/src/installer/installer_interface.rs b/crates/shirabe/src/installer/installer_interface.rs
index 3056429..20fdb2c 100644
--- a/crates/shirabe/src/installer/installer_interface.rs
+++ b/crates/shirabe/src/installer/installer_interface.rs
@@ -1,5 +1,7 @@
 //! ref: composer/src/Composer/Installer/InstallerInterface.php
 
+use crate::installer::BinaryPresenceInterface;
+use crate::installer::PluginInstaller;
 use crate::package::PackageInterfaceHandle;
 use crate::repository::InstalledRepositoryInterface;
 use shirabe_php_shim::PhpMixed;
@@ -55,6 +57,14 @@ pub trait InstallerInterface: std::fmt::Debug {
 
     fn get_install_path(&self, package: PackageInterfaceHandle) -> Option<String>;
 
+    fn as_binary_presence_interface(&mut self) -> Option<&mut dyn BinaryPresenceInterface> {
+        None
+    }
+
+    fn as_plugin_installer_mut(&mut self) -> Option<&mut PluginInstaller> {
+        None
+    }
+
     fn clone_box(&self) -> Box<dyn InstallerInterface> {
         todo!()
     }