PR Shepherd Contract (GitHub adapter)

The GitHub binding for the provider-neutral shepherd contract (src/shepherd_contract.py). The contract defines WHAT a shepherd task is responsible for and WHICH observed events count; this skill supplies the GitHub-specific half:

• Observation — observe(repo, number) reads live PR state via the GitHub CLI (gh api) and emits one ObservedEvent (merged / closed unmerged / updated).
• Actor resolution — resolve_actor(repo, number) uses the last non-merge commit's author email (git.commit_author_email), not the account login, because several actors can push under one login.
• Persistence — save(task_id, scope, state) / load(task_id) / resume(task_id) keep the durable contract record under <workspace>/state/shepherd/, create-or-advance only (never rebind), so a different process can pick the objective up later.

Usage

Import from the skill's scripts directory (the module bootstraps src/ onto sys.path itself):

import sys, pathlib
sys.path.insert(0, str(repo_root / "skills" / "pr-shepherd-contract" / "scripts"))
import shepherd_github as g

scope = g.scope_for("owner/repo", 123, g.resolve_actor("owner/repo", 123))
g.save("task-abc", scope, "waiting", "shepherding PR 123")
# ... later, any process:
state, why = g.resume("task-abc")

Tests: tests/shepherd-github-durability.test.py, tests/shepherd-github-integrity.test.py (contract policy itself: tests/shepherd-contract-admission.test.py).