Use ApiPathString in app-server filesystem permission paths (#28367)

## Why

Clients running an app-server on one OS and an exec-server on another OS
need to be able to pass sandbox config to app-server that refers to
resources on the executor's foreign OS.

## What

`AbsolutePathBuf` can't represent these paths and we don't want users to
be exposed to `PathUri` yet, so this moves the public app-server API to
be expressed in terms of `ApiPathString`.

Stacked on #28165.

- change app-server v2 filesystem permission paths, including legacy
read/write roots, to `ApiPathString`
- localize API paths through `PathUri` when converting into the current
native core permission types
- make path-bearing permission conversions fallible and surface
localization failures instead of silently treating malformed grants as
ordinary denials
- propagate conversion failures through app-server and TUI approval
handling
- regenerate the app-server JSON and TypeScript schemas
- leave migration TODOs on native-path conversions so they can be
removed once core permission paths use `PathUri`

codex-rs/tui/src/bottom_pane/approval_overlay.rs

@@ -1000,7 +1000,7 @@ fn format_file_system_entry_paths<'a>(
 ) -> String {
     entries
         .map(|entry| match &entry.path {
-            FileSystemPath::Path { path } => format!("`{}`", path.display()),
+            FileSystemPath::Path { path } => format!("`{path}`"),
             FileSystemPath::GlobPattern { pattern } => format!("glob `{pattern}`"),
             FileSystemPath::Special { value } => format!("`{}`", special_path_label(value)),
         })