Show plugin hooks in plugin details (#21447)

Supersedes the abandoned #19859, rebuilt on latest `main`.

# Why

PR #19705 adds discovery for hooks bundled with plugins, but `/plugins`
still only shows skills, apps, and MCP servers. This follow-up makes
bundled hooks visible in the same plugin detail view so users can
inspect the full plugin surface in one place.

We also need `PluginHookSummary` to populate Plugin Hooks in the app;
`hooks/list` is not enough there because plugin detail needs to show
hooks for disabled plugins too.

# What

- extend `plugin/read` with `PluginHookSummary` entries for bundled
hooks
- summarize plugin hooks while loading plugin details
- render a `Hooks` row in the `/plugins` detail popup

<img width="3456" height="848" alt="CleanShot 2026-04-27 at 11 45 34@2x"
src="https://github.com/user-attachments/assets/fe3a38d6-a260-4351-8513-fb04c93d725b"
/>

codex-rs/tui/src/chatwidget/tests/helpers.rs

@@ -1505,6 +1505,7 @@ pub(super) fn plugins_test_detail(
     summary: PluginSummary,
     description: Option<&str>,
     skills: &[&str],
+    hooks: &[(codex_app_server_protocol::HookEventName, usize)],
     apps: &[(&str, bool)],
     mcp_servers: &[&str],
 ) -> PluginDetail {
@@ -1526,6 +1527,18 @@ pub(super) fn plugins_test_detail(
                 enabled: true,
             })
             .collect(),
+        hooks: hooks
+            .iter()
+            .enumerate()
+            .flat_map(|(event_index, (event_name, handler_count))| {
+                (0..*handler_count).map(move |handler_index| {
+                    codex_app_server_protocol::PluginHookSummary {
+                        key: format!("plugin:{event_index}:{handler_index}"),
+                        event_name: *event_name,
+                    }
+                })
+            })
+            .collect(),
         apps: apps
             .iter()
             .map(|(name, needs_auth)| AppSummary {

codex-rs/tui/src/chatwidget/tests/popups_and_settings.rs

@@ -656,6 +656,10 @@ async fn plugin_detail_popup_snapshot_shows_install_actions_and_capability_summa
                 summary,
                 Some("Turn Figma files into implementation context."),
                 &["design-review", "extract-copy"],
+                &[
+                    (codex_app_server_protocol::HookEventName::PreToolUse, 1),
+                    (codex_app_server_protocol::HookEventName::Stop, 2),
+                ],
                 &[("Figma", true), ("Slack", false)],
                 &["figma-mcp", "docs-mcp"],
             ),
@@ -696,6 +700,10 @@ async fn plugin_detail_popup_hides_disclosure_for_installed_plugins() {
                 summary,
                 Some("Turn Figma files into implementation context."),
                 &["design-review", "extract-copy"],
+                &[
+                    (codex_app_server_protocol::HookEventName::PreToolUse, 1),
+                    (codex_app_server_protocol::HookEventName::Stop, 2),
+                ],
                 &[("Figma", true), ("Slack", false)],
                 &["figma-mcp", "docs-mcp"],
             ),