Add tng capability to macOS VM workers #58

Summary #

• record the optional preinstalled tng version when validating a macOS VM base
• advertise that version through the worker protocol and match agent workflows using an explicit version constraint
• expose /usr/local/bin/tng to VM jobs without rebuilding tng for each job
• require tng 0.7.x in the unit-test workflow and comment the measured test duration when a Pull Request input is provided
• pin the worker protocol to the corresponding core commit

Verification #

The scheduler accepts tng 0.7.x workers for the configured range and rejects missing, invalid, and 0.8.x capabilities. The updated protocol fixtures round-trip between Go and Swift, and the spindle-agent unit and core interoperability suites pass.

Live self-hosted verification has not yet been performed because it requires preparing and validating a new VM base with the released tng 0.7.0.