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/Cargo.lock

@@ -2109,6 +2109,7 @@ dependencies = [
  "codex-shell-command",
  "codex-utils-absolute-path",
  "codex-utils-cargo-bin",
+ "codex-utils-path-uri",
  "inventory",
  "pretty_assertions",
  "rmcp",
@@ -4050,6 +4051,7 @@ dependencies = [
  "codex-utils-home-dir",
  "codex-utils-oss",
  "codex-utils-path",
+ "codex-utils-path-uri",
  "codex-utils-plugins",
  "codex-utils-sandbox-summary",
  "codex-utils-sleep-inhibitor",