Sync reviewed GPU engineering changes and dependency pins

[NiSeullent]

Sync the reviewed GPU module with the current engineering packaging milestone while preserving its existing public history. Sibling dependencies use explicit immutable revisions. Only reviewed implementation, tests and build scaffolding are included; internal research and raw proprietary evidence remain excluded.

This is a packaging/development update. It does not establish macOS 27 boot, a functioning guest Metal driver, physical installation or qualified real Intel Mac support.

Changed paths:

• .github/workflows/ci.yml
• Cargo.toml
• src/command_executor.rs
• src/display_path_freeze.rs
• src/lib.rs
• src/metal_accel_probe.rs
• src/metal_acceptance.rs
• src/metal_d10_gates.rs
• src/metal_guest_probe.rs
• src/metal_public_abi.rs
• src/metal_transport.rs
• tests/gpu_render_path.rs
• tests/metal_acceptance_contract.rs

Validation: focused module tests and builds are recorded by the integration task; standalone CI verifies the published dependency revisions before merge.