chore(stamphog): sync engine from upstream and raise line ceiling to 1200

[charlesvien]

Problem

Stamphog's vendored engine had drifted ~2 months behind PostHog/posthog's tools/pr-approval-agent (local copy was pinned at May's c456bb59b67 plus two cherry-picks), and the 1000-line auto-review ceiling was rejecting PRs we want reviewed.

Changes

Re-vendors the engine at upstream b49088aa600, following the sync protocol upstream documents (re-copy, re-apply documented local changes). This brings the .stamphog/ policy extraction, author familiarity, manifest-risk scanning, sticky non-approve comments, bot-author hard gate, in-flight reviewer-bot waits, provenance trailers and the tools/owners resolver package. The workflow is updated to match, keeping this repo's local differences: Stamphog label, main ref and approvals posted by github-actions[bot] (the identity confirmed to count toward our branch ruleset). All local changes are documented in the vendored README per the upstream protocol.

On top of the sync, size_gate.max_lines goes to 1200 (was 1000 locally, 800 upstream).

How did you test this?

• pytest tools/pr-approval-agent (439 passed) and pytest tools/owners/tests (92 passed)
• uv run tools/pr-approval-agent/review_pr.py 3666 --dry-run against this repo: gates, policy load and the no-ownership-files path all work end to end

Automatic notifications

• Publish to changelog?
• Alert Sales and Marketing teams?

[trunk-io]

😎 This pull request was merged.

[greptile-apps]

_{Reviews (1): Last reviewed commit: "raise stamphog line ceiling to 1200" | Re-trigger Greptile}

[veria-ai]

PR overview

All previously flagged issues have been addressed. No open security concerns remain on this pull request.

Security review

No open security issues remain on this pull request.

Fixed/addressed: 1 · PR risk: 0/10