Recognize uvx lint evidence for PR guards

[dmoliveira]

Summary

• teach the gateway validation matcher to treat uvx ruff check and uv run ruff check as lint evidence
• add regression coverage for the matcher and the PR body evidence guard so recorded uvx ruff runs satisfy PR validation requirements
• regenerate the gateway-core matcher dist output to keep runtime behavior aligned with source and tests

Validation

• npm test in plugin/gateway-core
• pre-commit hook suite passed during commit creation