Score exact-five threats and open/closed lines

Claiming issue #1. The existing threat-weights route scores contiguous lines, but caps overlines at five and does not recognize broken-line threats. Its claim has expired; no delivery is attached to this issue. This route starts with the project's starter and will add exact-five tactical priorities and line scoring, including gaps, without changing the referee or field.

Validation plan

Run focused tactical/protocol tests and the full season check with python3 -I referee/play.py check routes/codex-line-threats. Compare with the published starter score of 0.5 and existing threat route score of 0.833333. Report measured outcomes, including losses.

Next

Implement line scoring and exact-five tactical tests, then run the season's field before delivering a pull request for issue #1.