Add Windows hook command overrides (#22159)

# Why

Managed hook configs need a shared cross-platform shape without making
the existing `command` field polymorphic. The common case is still one
command string, with Windows needing a different entrypoint only when
the runtime is actually Windows.

Keeping `command` as the portable/default path and adding an optional
Windows override keeps the config easier to read, preserves the existing
scalar shape for non-Windows users, and avoids forcing every caller into
a `{ unix, windows }` object when only one platform needs special
handling.

# What

- Add optional `command_windows` / `commandWindows` alongside the
existing hook `command` field.
- Resolve `command_windows` only on Windows during hook discovery; other
platforms continue to use `command` unchanged.
- Keep trust hashing aligned to the effective command selected for the
current runtime.

# Docs

The Codex hooks/config reference should document `command_windows` as
the Windows-only override for command hooks.

codex-rs/app-server/src/request_processors/config_processor.rs

@@ -515,11 +515,13 @@ fn map_hook_handler_to_api(handler: CoreHookHandlerConfig) -> ConfiguredHookHand
     match handler {
         CoreHookHandlerConfig::Command {
             command,
+            command_windows,
             timeout_sec,
             r#async,
             status_message,
         } => ConfiguredHookHandler::Command {
             command,
+            command_windows,
             timeout_sec,
             r#async,
             status_message,

codex-rs/app-server/tests/suite/v2/hooks_list.rs

@@ -53,6 +53,7 @@ fn command_hook_hash(
             matcher: matcher.map(ToOwned::to_owned),
             hooks: vec![codex_config::HookHandlerConfig::Command {
                 command: command.to_string(),
+                command_windows: None,
                 timeout_sec: Some(timeout_sec),
                 r#async: false,
                 status_message: status_message.map(ToOwned::to_owned),