[daveshanley]

Add a lightweight way to check API changes in a pull request and move to OpenAPI Doctor when workspace history, diagnostics, or pipeline controls are needed.

• Add opt-in compact Markdown with semantic counts, bounded Doctor highlights, and completed-result JSON. Existing report defaults remain unchanged.
• Add a GitHub Action with a Go runner and Go integration tests. It compares exact revisions, applies base-revision rules, writes a job summary, and retains full report artifacts before enforcing policy.
• Use read-only repository access, capture tool output, and ignore checkout-local rule overrides. The Action needs no Doctor account and sends no specs to Doctor.

Validation: command and full Go suites pass; real-CLI Action tests cover policy, invalid input, revision-scoped references, base rules, and numeric output counts; actionlint passes. Independent correctness and de-slop reviews found no material issues in the Go replacement. All eight hosted checks pass on 38ef463, including the five-case Action matrix using the Go runner.

Risk: medium. The new Action executes the existing parser on PR specifications and stores report artifacts under normal repository access controls. It compiles the CLI and runner from the pinned Action source, which adds setup time. A separate fork PR and authenticated Doctor onboarding have not been tested. Shared-engine rule parity is outside this PR.

See Action setup for inputs, permissions, and version pinning.

[daveshanley]

@greptileai review

Please review the completed lightweight Action and compact report at 36baa3c8688342aeb2e9036abdd20ab53d49573a. All eight hosted checks pass. The latest commit adds the missing compact highlight for whole-path removals.