What changed

Rebrands the public contributor-check PR/issue comment as AgentTrust-owned while keeping the existing pinned Microsoft Agent Governance Toolkit implementation for the risk checks.

The composite action now runs a small post-processing helper after the AGT check. The helper finds the existing contributor-check comment by its hidden idempotency marker, preserves that marker so future runs update the same comment, and replaces the visible footer with:

Automated check by AgentTrust Contributor Check

Why

The check is part of the AgentTrust repository workflow, so the visible automation should read as AgentTrust infrastructure. The upstream AGT dependency remains acknowledged in the action description and implementation comments, preserving attribution without exposing Microsoft AGT as the user-facing brand on every PR.

Validation

• python3 -m py_compile .github/actions/contributor-check/brand_comment.py
• Local _branded_body smoke test confirmed:
  • hidden marker is preserved
  • visible footer changes to AgentTrust
  • visible AGT Contributor Check footer is removed
• ruby -e "require 'yaml'; YAML.load_file('.github/actions/contributor-check/action.yml')"
• git diff --check