fix(computer-use): separate permission request from settings

[Tryanks]

Summary

• request native macOS consent without opening System Settings in the same click
• turn the next explicit action into Open System Settings and recheck permissions when tcode becomes active
• scope relaunch continuity to Screen Recording, clear denied flows, and ignore stale denied markers at startup
• document Apple guidance and add regression coverage for the permission state machine and marker lifecycle

Testing

• cargo fmt --all --check
• cargo clippy --workspace --all-targets --locked -- -D warnings
• cargo test --workspace --locked