permissions: remove macOS seatbelt extension profiles (#15918)

## Why

`PermissionProfile` should only describe the per-command permissions we
still want to grant dynamically. Keeping
`MacOsSeatbeltProfileExtensions` in that surface forced extra macOS-only
approval, protocol, schema, and TUI branches for a capability we no
longer want to expose.

## What changed

- Removed the macOS-specific permission-profile types from
`codex-protocol`, the app-server v2 API, and the generated
schema/TypeScript artifacts.
- Deleted the core and sandboxing plumbing that threaded
`MacOsSeatbeltProfileExtensions` through execution requests and seatbelt
construction.
- Simplified macOS seatbelt generation so it always includes the fixed
read-only preferences allowlist instead of carrying a configurable
profile extension.
- Removed the macOS additional-permissions UI/docs/test coverage and
deleted the obsolete macOS permission modules.
- Tightened `request_permissions` intersection handling so explicitly
empty requested read lists are preserved only when that field was
actually granted, avoiding zero-grant responses being stored as active
permissions.

codex-rs/sandboxing/src/lib.rs

@@ -1,13 +1,10 @@
 #[cfg(target_os = "linux")]
 mod bwrap;
 pub mod landlock;
-pub mod macos_permissions;
 mod manager;
 pub mod policy_transforms;
 #[cfg(target_os = "macos")]
 pub mod seatbelt;
-#[cfg(target_os = "macos")]
-mod seatbelt_permissions;
 
 #[cfg(target_os = "linux")]
 pub use bwrap::find_system_bwrap_in_path;