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/hooks/src/engine/mod.rs

@@ -8,6 +8,8 @@ use std::collections::HashMap;
 
 use codex_config::ConfigLayerStack;
 use codex_plugin::PluginHookSource;
+use codex_protocol::protocol::HookEventName;
+use codex_protocol::protocol::HookHandlerType;
 use codex_protocol::protocol::HookRunSummary;
 use codex_protocol::protocol::HookSource;
 use codex_utils_absolute_path::AbsolutePathBuf;
@@ -67,6 +69,20 @@ impl ConfiguredHandler {
     }
 }
 
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct HookListEntry {
+    pub event_name: HookEventName,
+    pub handler_type: HookHandlerType,
+    pub matcher: Option<String>,
+    pub command: Option<String>,
+    pub timeout_sec: u64,
+    pub status_message: Option<String>,
+    pub source_path: AbsolutePathBuf,
+    pub source: HookSource,
+    pub plugin_id: Option<String>,
+    pub display_order: i64,
+}
+
 #[derive(Clone)]
 pub(crate) struct ClaudeHooksEngine {
     handlers: Vec<ConfiguredHandler>,