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/bundles.rs

@@ -542,7 +542,7 @@ pub fn list_installed_bundles() -> Result<()> {
     let store = BundleStore::load()?;
     let rows = bundle_list_rows(&store, &paths::config_dir());
     if rows.is_empty() {
-        println!("No bundles installed. Install one with `coyote --install-from <git-url>`.");
+        println!("No bundles installed. Install one with `coyote --install <git-url>`.");
         return Ok(());
     }