Ensure Required Reference Check Emits

Why

The main ruleset requires the typecheck + full test suite status check, but the workflow that emits that context is path-filtered. PRs that do not touch the filtered paths can become blocked because the required context never appears.

What Changes

• Make the reference-implementation workflow trigger for every pull request and merge-group.
• Keep the required job/context name stable.
• Add a path classifier inside the job so non-reference PRs complete the required context successfully without running the heavy suite.

Capabilities

Modified:

• reference-implementation-governance

Impact

• Docs/research/policy PRs get an explicit required check result instead of a missing required context.
• Reference-impacting PRs still run the same typecheck and test suite.
• This does not deploy, release, or mutate live data.