Mechanize pull request state collection

[ariobarin]

Summary

• add a read-only GitHub GraphQL collector for one normalized pull request state packet
• bind checks, reviews, and inline comments to the current head SHA and surface stale evidence
• expose pagination truncation explicitly instead of silently claiming complete inspection
• default to compact body excerpts with full comment bodies available through --include-bodies
• update the PR review skill to use the collector while preserving independent review and merge-authority boundaries

Usage

python codex/skills/pr-review-loop/scripts/collect-pr-state.py --repo owner/name --pr 123

Add --include-bodies when complete review or comment text is needed. A packet with complete: false requires pagination before a completeness claim.

Validation

• live snapshot against ariobarin/compass#285 returned the expected head SHA and five checks
• python scripts/test-pr-state.py
• python scripts/test-review-bundle.py
• python scripts/validate-policy-contracts.py
• python scripts/test-compass-architecture.py
• git diff --check
• .\scripts\doctor.ps1
• pwsh -NoProfile -File .\scripts\test-install-roundtrip.ps1

The install round trip was rerun under PowerShell 7 after Windows PowerShell 5.1 rejected the repository's existing utf8NoBOM encoding option before reaching this change.