feat(governance): enforce author-dependent Governance Council approval rules

[carolinerg1]

Description

Simplify the Governance Council (GC) dynamic approval rules in pr_validator.py to match the new policy.

• If the PR author is in the GC, only 1 GC approval is required.
• If the PR author is not in the GC, the default min_approvals from the repository's rules configuration is respected
• Updated unit tests to match the simplified logic and added a test case to verify that non-GC authors respect YAML configurations requiring 1 approval.

Category (Required)

Please select one or more categories that apply to this change.

• Core Protocol: Changes to the base communication layer, global context, or breaking refactors. (Requires Technical Council approval)
• Governance/Contributing: Updates to GOVERNANCE.md, CONTRIBUTING.md, or CODEOWNERS. (Requires Governance Council approval)
• Capability: New schemas (Discovery, Cart, etc.) or extensions. (Requires Maintainer approval)
• Documentation: Updates to README, or documentations regarding schema or capabilities. (Requires Maintainer approval)
• Infrastructure: CI/CD, Linters, or build scripts. (Requires DevOps Maintainer approval)
• Maintenance: Version bumps, lockfile updates, or minor bug fixes. (Requires DevOps Maintainer approval)
• SDK: Language-specific SDK updates and releases. (Requires DevOps Maintainer approval)
• Samples / Conformance: Maintaining samples and the conformance suite. (Requires Maintainer approval)
• UCP Schema: Changes to the ucp-schema tool (resolver, linter, validator). (Requires Maintainer approval)
• Community Health (.github): Updates to templates, workflows, or org-level configs. (Requires DevOps Maintainer approval)

Related Issues

Checklist

• I have followed the Contributing Guide (including Conventional Commits title requirements and ! for breaking changes).
• I have updated the documentation (if applicable).
• My changes pass all local linting and formatting checks.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• (For Core/Capability) I have included/updated the relevant JSON schemas.
• I have regenerated Python Pydantic models by running generate_models.sh under python_sdk.

Screenshots / Logs (if applicable)

[amithanda]

len(approver_usernames) < require_total_approvals

Can you please double check and confirm the logic here?
I haven't looked too closely but I think there may be an edge-case bug here: approver_usernames can contain non-approving reviewers (e.g., users who only commented or requested changes), causing len(approver_usernames) to pass even when there isn't a second actual approval.

To fix this, we should count distinct valid approvals (excluding the PR author):

total_valid_approvals = len([u for u in approver_usernames if u != author])
if total_valid_approvals < require_total_approvals:
    is_satisfied = False

[damaz91]

Thanks for double-checking @amithanda - that’s actually already handled upstream in _get_all_approvers_and_assigned_usernames():

1. approver_usernames is only populated from reviews where state == ReviewState.APPROVED (commenters and change requestors are placed into assigned_usernames instead).
2. The author is already filtered out there (if user != pr.author), so approver_usernames is guaranteed to contain only distinct, non-author approving reviewers.

Because of that, len(approver_usernames) accurately reflects the total number of distinct valid approvals on the PR.