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/app-server/tests/suite/v2/plugin_read.rs

@@ -17,6 +17,7 @@ use axum::http::Uri;
 use axum::http::header::AUTHORIZATION;
 use axum::routing::get;
 use codex_app_server_protocol::AppInfo;
+use codex_app_server_protocol::HookEventName;
 use codex_app_server_protocol::JSONRPCResponse;
 use codex_app_server_protocol::PluginAuthPolicy;
 use codex_app_server_protocol::PluginInstallPolicy;
@@ -778,6 +779,7 @@ async fn plugin_read_returns_plugin_details_with_bundle_contents() -> Result<()>
     std::fs::create_dir_all(repo_root.path().join(".git"))?;
     std::fs::create_dir_all(repo_root.path().join(".agents/plugins"))?;
     std::fs::create_dir_all(plugin_root.join(".codex-plugin"))?;
+    std::fs::create_dir_all(plugin_root.join("hooks"))?;
     std::fs::create_dir_all(plugin_root.join("skills/thread-summarizer"))?;
     std::fs::create_dir_all(plugin_root.join("skills/chatgpt-only"))?;
     std::fs::write(
@@ -881,12 +883,44 @@ description: Visible only for ChatGPT
       "command": "demo-server"
     }
   }
+}"#,
+    )?;
+    std::fs::write(
+        plugin_root.join("hooks/hooks.json"),
+        r#"{
+  "hooks": {
+    "SessionStart": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "echo startup"
+          }
+        ]
+      }
+    ],
+    "PreToolUse": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "echo first"
+          },
+          {
+            "type": "command",
+            "command": "echo second"
+          }
+        ]
+      }
+    ]
+  }
 }"#,
     )?;
     std::fs::write(
         codex_home.path().join("config.toml"),
         r#"[features]
 plugins = true
+plugin_hooks = true
 
 [[skills.config]]
 name = "demo-plugin:thread-summarizer"
@@ -894,6 +928,9 @@ enabled = false
 
 [plugins."demo-plugin@codex-curated"]
 enabled = true
+
+[hooks.state."demo-plugin@codex-curated:hooks/hooks.json:pre_tool_use:0:0"]
+enabled = false
 "#,
     )?;
     write_installed_plugin(&codex_home, "codex-curated", "demo-plugin")?;
@@ -980,6 +1017,23 @@ enabled = true
         "Summarize email threads"
     );
     assert!(!response.plugin.skills[0].enabled);
+    assert_eq!(
+        response.plugin.hooks,
+        vec![
+            codex_app_server_protocol::PluginHookSummary {
+                key: "demo-plugin@codex-curated:hooks/hooks.json:pre_tool_use:0:0".to_string(),
+                event_name: HookEventName::PreToolUse,
+            },
+            codex_app_server_protocol::PluginHookSummary {
+                key: "demo-plugin@codex-curated:hooks/hooks.json:pre_tool_use:0:1".to_string(),
+                event_name: HookEventName::PreToolUse,
+            },
+            codex_app_server_protocol::PluginHookSummary {
+                key: "demo-plugin@codex-curated:hooks/hooks.json:session_start:0:0".to_string(),
+                event_name: HookEventName::SessionStart,
+            },
+        ]
+    );
     assert_eq!(response.plugin.apps.len(), 1);
     assert_eq!(response.plugin.apps[0].id, "gmail");
     assert_eq!(response.plugin.apps[0].name, "gmail");