feat: rename install flags and unify .install dispatch

--install now takes a git URL or an installed bundle name: categories
are redirected to the new --install-builtins, installed names become
implicit updates, and source-shaped values install remotely. The old
--install-from keeps its exact behavior as a hidden deprecated alias.
The REPL's .install gains the same unified dispatch while keeping
.install <category> and .install remote <url> back-compat.

src/config/mod.rs

@@ -33,7 +33,8 @@ pub use self::app_state::AppState;
 pub use self::bundles::list_installed_bundles;
 pub use self::input::Input;
 pub use self::install_remote::{
-    install_remote, install_remote_from_repl_args, uninstall_bundle, update_bundle,
+    install_or_update, install_or_update_from_repl_args, install_remote,
+    install_remote_from_repl_args, uninstall_bundle, update_bundle,
 };
 pub use self::macro_policy::{
     MacroAllowlistLevel, MacroPolicy, MacroSource, MacroState, RESERVED_MACRO_NAMES, ResolvedMacro,