Propagate runtime permission profiles

[evawong-oai]

Summary

Propagate active runtime permission profiles through embedded turn start paths so later sandbox checks use the current policy.

Scope

1. Pass runtime permission profiles through thread routing.
2. Preserve legacy sandbox behavior for remote turns.
3. Add focused coverage for embedded and remote turn start cases.

Reviewer Focus

1. This PR is separate because it updates active session permission flow, not platform sandbox implementation.
2. Embedded turns should receive the active runtime profile when one exists.
3. Remote turns should keep the existing legacy sandbox behavior.

Stack

1. Policy primitive: Add workspace metadata protection policy primitive #19846
2. macOS Seatbelt enforcement: Enforce workspace metadata protections in Seatbelt #19847
3. Shell preflight UX: Add workspace metadata shell preflight #19848
4. Runtime permission propagation: this PR
5. Linux bubblewrap enforcement: Enforce workspace metadata protections in Linux sandbox #19852

Validation

1. cargo test --manifest-path codex-rs/Cargo.toml -p codex-tui app_server_session
2. cargo test --manifest-path codex-rs/Cargo.toml -p codex-tui thread_routing
3. cargo fmt --manifest-path codex-rs/Cargo.toml --package codex-tui