refactor(installed-repository): make add_repository infallible with assert

The repository type check was an internal invariant, not a recoverable
error condition. Replace the Result-returning validation with an
assert!, matching Composer's design where add_repository throws only on
a programming error, and drop the now-unneeded error handling at call
sites.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

2 files changed, 7 insertions, 9 deletions

diff --git a/crates/shirabe/src/command/base_dependency_command.rs b/crates/shirabe/src/command/base_dependency_command.rs
index 4a5b854..a9ed7cd 100644
--- a/crates/shirabe/src/command/base_dependency_command.rs
+++ b/crates/shirabe/src/command/base_dependency_command.rs
@@ -166,13 +166,11 @@ pub trait BaseDependencyCommand: BaseCommand {
                 &needle,
                 FindPackageConstraint::String(text_constraint.clone()),
             )? {
-                installed_repo.add_repository(
-                    crate::repository::RepositoryInterfaceHandle::new(
-                        InstalledArrayRepository::new_with_packages(vec![
-                            crate::package::PackageInterfaceHandle::dup(&r#match),
-                        ])?,
-                    ),
-                )?;
+                installed_repo.add_repository(crate::repository::RepositoryInterfaceHandle::new(
+                    InstalledArrayRepository::new_with_packages(vec![
+                        crate::package::PackageInterfaceHandle::dup(&r#match),
+                    ])?,
+                ));
             } else if PlatformRepository::is_platform_package(&needle) {
                 let parser = VersionParser::new();
                 let platform_constraint = parser.parse_constraints(&text_constraint)?;
@@ -189,7 +187,7 @@ pub trait BaseDependencyCommand: BaseCommand {
                                     .into(),
                             ])?,
                         ),
-                    )?;
+                    );
                 }
             } else {
                 self.get_io().write_error(&format!(
diff --git a/crates/shirabe/src/command/show_command.rs b/crates/shirabe/src/command/show_command.rs
index e14ab15..859ba97 100644
--- a/crates/shirabe/src/command/show_command.rs
+++ b/crates/shirabe/src/command/show_command.rs
@@ -270,7 +270,7 @@ impl ShowCommand {
                         .get_repository_manager()
                         .borrow()
                         .get_local_repository(),
-                )?;
+                );
                 installed_repo = RepositoryInterfaceHandle::new(ir);
             } else {
                 let default_repos =