SpecRail Write Tech Spec

Use this skill for the technical half of the write_spec route.

Steps

1. Read the linked issue and specs/GH<issue-number>/product.md.
2. Read the relevant tech spec template from templates/<locale>/tech_spec.md or templates/tech_spec.md.
3. Run the local gate when available:

python3 checks/route_gate.py --repo . --route write_spec --issue <issue-number> --state ready_to_spec --json