Summary

• harden BoxLite macOS seatbelt policy to deny-by-default with explicit allowlists and dynamic path grants
• keep existing network toggle semantics and runtime binary lookup behavior
• add macOS jailer integration coverage for deny-profile lifecycle behavior
• fix deny-test cleanup semantics by treating NotFound from explicit runtime.remove(..., true) as acceptable when startup failure cleanup already removed runtime registration

Commit split

1. harden macOS seatbelt deny-default policy and runtime paths
2. add macOS jailer integration coverage and cleanup semantics

Validation

• cargo fmt --check ✅
• cargo clippy -p boxlite --tests -- -D warnings ✅
• BOXLITE_RUNTIME_DIR=$(pwd)/target/boxlite-runtime cargo test -p boxlite --test jailer jailer_enabled_box_starts_and_executes -- --test-threads=1 --nocapture ✅
• BOXLITE_RUNTIME_DIR=$(pwd)/target/boxlite-runtime cargo test -p boxlite --test jailer jailer_enabled_custom_profile_deny_boxes_subpath_blocks_start -- --test-threads=1 --nocapture ✅
• BOXLITE_RUNTIME_DIR=$(pwd)/target/boxlite-runtime cargo test -p boxlite --test jailer jailer_disabled_with_same_profile_still_starts -- --test-threads=1 --nocapture ✅
• cargo test -p boxlite jailer::sandbox::seatbelt::tests:: -- --nocapture ✅