feat: add --help guides to the .install and .uninstall REPL commands

.install --help and .uninstall --help print a usage guide covering the
owner/repo shorthand, --git-host, --filter, --force, ref pinning, and
the bundle lifecycle; both usage error lines now point at --help. Tab
completion offers --help for both commands and --git-host on the first
.install argument, and the unified install parser accepts flags in any
argument position so completed flags work wherever they are inserted.
The empty .list bundles message now shows the REPL install form
alongside the CLI one.

src/repl/mod.rs

@@ -875,9 +875,10 @@ pub async fn run_repl_command(
                 ReplInstallDispatch::Unified(value) => {
                     config::install_or_update_from_repl_args(value)?;
                 }
+                ReplInstallDispatch::Help => println!("{}", repl_install_help()),
                 ReplInstallDispatch::Usage => println!(
                     "Usage: .install <{}> | .install <git-url|owner/repo|installed-bundle> \
-                         [--git-host <host>] [--filter <cat>] [--force]",
+                         [--git-host <host>] [--filter <cat>] [--force] (see `.install --help`)",
                     AssetCategory::NAMES.join("|")
                 ),
             },
@@ -1198,8 +1199,13 @@ pub async fn run_repl_command(
                 }
             },
             ".uninstall" => match parse_repl_uninstall(args) {
-                Some((name, assume_yes)) => config::uninstall_bundle(&name, assume_yes)?,
-                None => println!("Usage: .uninstall <bundle-name> [--yes]"),
+                ReplUninstallDispatch::Run(name, assume_yes) => {
+                    config::uninstall_bundle(&name, assume_yes)?
+                }
+                ReplUninstallDispatch::Help => println!("{}", repl_uninstall_help()),
+                ReplUninstallDispatch::Usage => {
+                    println!("Usage: .uninstall <bundle-name> [--yes] (see `.uninstall --help`)")
+                }
             },
             ".list" => match args {
                 Some(args) => {
@@ -1573,11 +1579,18 @@ fn unknown_command() -> Result<()> {
 enum ReplInstallDispatch<'a> {
     Builtins(AssetCategory),
     Unified(&'a str),
+    Help,
     Usage,
 }
 
 fn parse_repl_install(args: Option<&str>) -> ReplInstallDispatch<'_> {
     let trimmed = args.map(str::trim).unwrap_or("");
+    if trimmed
+        .split_whitespace()
+        .any(|token| token == "--help" || token == "-h")
+    {
+        return ReplInstallDispatch::Help;
+    }
     let mut parts = trimmed.splitn(2, char::is_whitespace);
     match parts.next() {
         Some(name) if !name.is_empty() => {
@@ -1592,19 +1605,65 @@ fn parse_repl_install(args: Option<&str>) -> ReplInstallDispatch<'_> {
     }
 }
 
-fn parse_repl_uninstall(args: Option<&str>) -> Option<(String, bool)> {
+fn repl_install_help() -> String {
+    format!(
+        r#"Install built-in assets, install a bundle from a Git source, or update an installed bundle.
+
+Usage:
+  .install <category>                  Reinstall built-in assets ({categories})
+  .install <owner/repo>[#ref]          Install a bundle from {default_host} (change the host with --git-host)
+  .install <git-url>[#ref]             Install a bundle from any Git URL, scp-style path, or local path
+  .install <installed-bundle>[#ref]    Update an installed bundle from its recorded source
+
+Flags:
+  --git-host <host>   Host the <owner/repo> shorthand expands against (default {default_host})
+  --filter <cat>      Restrict a remote install to one category ({filters})
+  --force             Overwrite all conflicts without prompting (remote installs only)
+
+Suffix #<ref> to pin a branch, tag, or commit. List installed bundles with
+`.list bundles`; remove one with `.uninstall <name>`."#,
+        categories = AssetCategory::NAMES.join("|"),
+        default_host = config::DEFAULT_GIT_HOST,
+        filters = config::InstallFilter::NAMES.join("|"),
+    )
+}
+
+fn repl_uninstall_help() -> String {
+    r#"Remove an installed bundle: delete the files it owns and the mcp.json entries it added.
+
+Usage:
+  .uninstall <bundle-name> [--yes]
+
+Flags:
+  --yes, -y   Skip the confirmation prompt
+
+Files you modified after install are prompted for individually and kept by
+default; --yes never deletes modified files. List installed bundles with
+`.list bundles`."#
+        .to_string()
+}
+
+#[derive(Debug, PartialEq)]
+enum ReplUninstallDispatch {
+    Run(String, bool),
+    Help,
+    Usage,
+}
+
+fn parse_repl_uninstall(args: Option<&str>) -> ReplUninstallDispatch {
     let mut assume_yes = false;
     let mut names = Vec::new();
     for token in args.unwrap_or("").split_whitespace() {
         match token {
+            "--help" | "-h" => return ReplUninstallDispatch::Help,
             "--yes" | "-y" => assume_yes = true,
-            other if other.starts_with('-') => return None,
+            other if other.starts_with('-') => return ReplUninstallDispatch::Usage,
             other => names.push(other),
         }
     }
     match names.as_slice() {
-        [name] => Some((name.to_string(), assume_yes)),
-        _ => None,
+        [name] => ReplUninstallDispatch::Run(name.to_string(), assume_yes),
+        _ => ReplUninstallDispatch::Usage,
     }
 }
 
@@ -1871,6 +1930,70 @@ mod tests {
         );
     }
 
+    #[test]
+    fn parse_repl_install_routes_help_from_any_position() {
+        assert_eq!(
+            parse_repl_install(Some("--help")),
+            ReplInstallDispatch::Help
+        );
+        assert_eq!(parse_repl_install(Some("-h")), ReplInstallDispatch::Help);
+        assert_eq!(
+            parse_repl_install(Some("agents --help")),
+            ReplInstallDispatch::Help
+        );
+        assert_eq!(
+            parse_repl_install(Some("owner/repo --help")),
+            ReplInstallDispatch::Help
+        );
+    }
+
+    #[test]
+    fn parse_repl_uninstall_routes_run_help_and_usage() {
+        assert_eq!(
+            parse_repl_uninstall(Some("my-bundle --yes")),
+            ReplUninstallDispatch::Run("my-bundle".to_string(), true)
+        );
+        assert_eq!(
+            parse_repl_uninstall(Some("my-bundle")),
+            ReplUninstallDispatch::Run("my-bundle".to_string(), false)
+        );
+        assert_eq!(
+            parse_repl_uninstall(Some("--help")),
+            ReplUninstallDispatch::Help
+        );
+        assert_eq!(
+            parse_repl_uninstall(Some("my-bundle -h")),
+            ReplUninstallDispatch::Help
+        );
+        assert_eq!(
+            parse_repl_uninstall(Some("--force my-bundle")),
+            ReplUninstallDispatch::Usage
+        );
+        assert_eq!(parse_repl_uninstall(None), ReplUninstallDispatch::Usage);
+    }
+
+    #[test]
+    fn repl_install_and_uninstall_help_text_cover_the_full_surface() {
+        let install = repl_install_help();
+        for needle in [
+            "--git-host",
+            "--filter",
+            "--force",
+            "#ref",
+            "owner/repo",
+            ".list bundles",
+        ] {
+            assert!(install.contains(needle), "install help missing {needle}");
+        }
+        let uninstall = repl_uninstall_help();
+        for needle in ["--yes", ".list bundles", "<bundle-name>"] {
+            assert!(
+                uninstall.contains(needle),
+                "uninstall help missing {needle}"
+            );
+        }
+    }
+
     #[test]
     fn builtin_command_names_are_sorted_deduped_first_words_without_dots() {
         let names = builtin_command_names();