docs: add Global LLM Worktree Rule to operating rules (#272)

Require mutations only from branches/ worktrees after proving project
root, cwd, branch, stable main-checkout branch, and session worktree
path. Surface in portable skill, runbooks, wiki, operator guide, and
start-issue template.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

tests/test_operator_guide.py

@@ -133,7 +133,7 @@ class TestControlPlaneGuide(GuideTestBase):
         for key in ("hard_stops", "fail_closed", "head_sha_pinning",
                     "merge_confirmation", "redaction", "separation",
                     "profile_switching", "identity_verification",
-                    "work_selection"):
+                    "work_selection", "global_worktree"):
             self.assertIn(key, rules)
         self.assertIn("MERGE PR", json.dumps(rules["merge_confirmation"]))
         self.assertTrue(rules["hard_stops"])

tests/test_review_proofs.py

@@ -1053,6 +1053,8 @@ class TestControllerHandoff(unittest.TestCase):
         self.assertIn("issue #182", skill)
         self.assertIn("## Work Selection Rule for LLMs", skill)
         self.assertIn("work already claimed", skill)
+        self.assertIn("## Global LLM Worktree Rule", skill)
+        self.assertIn("branches/", skill)
 
     def test_handoff_rejects_none_workspace_mutations_when_local_edits_exist(self):
         # 1. Workspace mutations: none is rejected when local_edits is True