PR #TBD - #1436: Parent Auto-PRs Must Not Inherit Host GitHub Tokens

The Remaining Identity-Routing Hole

Child dispatch already removed ambient GitHub tokens, but the parent daemon's auto-finalization path still copied its full environment. When a role App token was unavailable, an inherited GH_TOKEN could make gh authenticate as the human operator.

What This PR Shipped

Parent auto-PR environments now remove GH_TOKEN and GITHUB_TOKEN before role-token resolution. A role token is injected only when one is available; host authentication remains an explicit opt-in. Merge-shaped jobs also skip automatic PR creation, so a merge operation cannot create a second PR from its worktree.

Verification

Regression tests cover missing role tokens, role-token precedence over an inherited host token, and merge jobs with changed worktrees. The targeted test command is:

pytest tests/test_agent_cli.py -k 'implement_1436_leftover_charter_patch_so' -v

What This Achieved on the Path to Autonomy

Parent and child GitHub-write paths now share the same fail-closed identity boundary: role-scoped credentials are used when available, and a human token cannot be selected accidentally.