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-protocol/schema/json/codex_app_server_protocol.schemas.json

@@ -12144,6 +12144,12 @@
               "null"
             ]
           },
+          "hooks": {
+            "items": {
+              "$ref": "#/definitions/v2/PluginHookSummary"
+            },
+            "type": "array"
+          },
           "marketplaceName": {
             "type": "string"
           },
@@ -12175,6 +12181,7 @@
         },
         "required": [
           "apps",
+          "hooks",
           "marketplaceName",
           "mcpServers",
           "skills",
@@ -12182,6 +12189,21 @@
         ],
         "type": "object"
       },
+      "PluginHookSummary": {
+        "properties": {
+          "eventName": {
+            "$ref": "#/definitions/v2/HookEventName"
+          },
+          "key": {
+            "type": "string"
+          }
+        },
+        "required": [
+          "eventName",
+          "key"
+        ],
+        "type": "object"
+      },
       "PluginInstallParams": {
         "$schema": "http://json-schema.org/draft-07/schema#",
         "properties": {