## 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.
## Summary
- move the pure sandbox policy transform helpers from `codex-core` into
`codex-sandboxing`
- move the corresponding unit tests with the extracted implementation
- update `core` and `app-server` callers to import the moved APIs
directly, without re-exports or proxy methods
## Testing
- cargo test -p codex-sandboxing
- cargo test -p codex-core sandboxing
- cargo test -p codex-app-server --lib
- just fix -p codex-sandboxing
- just fix -p codex-core
- just fix -p codex-app-server
- just fmt
- just argument-comment-lint
