feat: expand owner/repo shorthand for --install with a --git-host flag

--install someuser/repo expands to https://github.com/someuser/repo;
--git-host overrides the default host and forces source interpretation
even when the value matches an installed bundle name. Two or more path
segments are accepted so nested GitLab-style groups work, and #ref
pinning applies to shorthand values. --uninstall resolves owner/repo
against recorded sources: a single match uninstalls, multiple matches
prompt an interactive selection showing each bundle's source, and
non-interactive runs bail instead of guessing.

src/main.rs

@@ -135,7 +135,12 @@ async fn main() -> Result<()> {
     }
 
     if let Some(value) = cli.install.as_deref() {
-        return config::install_or_update(value, cli.filter, cli.install_force);
+        return config::install_or_update(
+            value,
+            cli.git_host.as_deref(),
+            cli.filter,
+            cli.install_force,
+        );
     }
 
     if let Some(spec) = cli.update_bundle.as_deref() {