Add hooks/list app-server RPC (#19778)

## Why

We need a way to list the available hooks to expose via the TUI and App
so users can view and manage their hooks

## What

- Adds `hooks/list` for one or more `cwd` values that returns discovered
hook metadata

## Stack

1. openai/codex#19705
2. This PR - openai/codex#19778
3. openai/codex#19840
4. openai/codex#19882

## Review Notes

The generated schema files account for most of the raw diff, these files
have the core change:

- `hooks/src/engine/discovery.rs` builds the inventory entries during
hook discovery while leaving runtime handlers focused on execution.
- `app-server/src/codex_message_processor.rs` wires `hooks/list` into
the app-server flow for each requested `cwd`.
- `app-server-protocol/src/protocol/v2.rs` defines the new v2
request/response payloads exposed on the wire.

### Core Changes

`core/src/plugins/manager.rs` adds `plugins_for_layer_stack(...)` so
`skills/list` and `hooks/list`can resolve plugin state for each
requested `cwd`

---------

Co-authored-by: Codex <noreply@openai.com>

codex-rs/app-server/README.md

@@ -196,6 +196,7 @@ Example with notification opt-out:
 - `experimentalFeature/enablement/set` — patch the in-memory process-wide runtime feature enablement for the currently supported feature keys (`apps`, `memories`, `plugins`, `remote_control`, `tool_search`, `tool_suggest`, `tool_call_mcp_elicitation`). For each feature, precedence is: cloud requirements > --enable <feature_name> > config.toml > experimentalFeature/enablement/set (new) > code default.
 - `collaborationMode/list` — list available collaboration mode presets (experimental, no pagination). This response omits built-in developer instructions; clients should either pass `settings.developer_instructions: null` when setting a mode to use Codex's built-in instructions, or provide their own instructions explicitly.
 - `skills/list` — list skills for one or more `cwd` values (optional `forceReload`).
+- `hooks/list` — list discovered hooks for one or more `cwd` values.
 - `marketplace/add` — add a remote plugin marketplace from an HTTP(S) Git URL, SSH Git URL, or GitHub `owner/repo` shorthand, then persist it into the user marketplace config. Returns the installed root path plus whether the marketplace was already present.
 - `marketplace/remove` — remove a configured marketplace by name from the user marketplace config, and delete its installed marketplace root when one exists.
 - `marketplace/upgrade` — upgrade all configured Git plugin marketplaces, or one named marketplace when `marketplaceName` is provided. Returns selected marketplace names, upgraded roots, and per-marketplace errors.
@@ -1452,6 +1453,43 @@ To enable or disable a skill by name:
 }
 ```
 
+Use `hooks/list` to fetch the discovered hooks for one or more `cwds`.
+
+```json
+{
+  "method": "hooks/list",
+  "id": 28,
+  "params": {
+    "cwds": ["/Users/me/project"]
+  }
+}
+```
+
+```json
+{
+  "id": 28,
+  "result": {
+    "data": [{
+      "cwd": "/Users/me/project",
+      "hooks": [{
+        "eventName": "pre_tool_use",
+        "handlerType": "command",
+        "matcher": "Bash",
+        "command": "python3 /Users/me/hook.py",
+        "timeoutSec": 5,
+        "statusMessage": "running hook",
+        "sourcePath": "/Users/me/.codex/config.toml",
+        "source": "user",
+        "pluginId": null,
+        "displayOrder": 0
+      }],
+      "warnings": [],
+      "errors": []
+    }]
+  }
+}
+```
+
 ## Apps
 
 Use `app/list` to fetch available apps (connectors). Each entry includes metadata like the app `id`, display `name`, `installUrl`, `branding`, `appMetadata`, `labels`, whether it is currently accessible, and whether it is enabled in config.