feat(guard): harden workflow against unattributed root WIP and pytest-disabled production guards (Closes #683)

Add shared workflow_scope_guard with typed blockers (blocker_kind +
exact_next_action) and force-on production enforcement under pytest.
Wire root/branches/scope checks through verify_preflight_purity and
mutation entrypoints (create_issue, comment_issue) without adopting the
rejected 300a4ca patterns (test-mode early-return, porcelain *.py filter).

Regression suite covers out-of-scope issue ownership, root diagnostic
edits, worktree bind success path, force-on under pytest, porcelain
integrity, monkeypatch resistance, real entrypoint fail-closed proof,
and durable failure recording.

tests/test_preflight_read_survival.py

@@ -76,13 +76,17 @@ class TestPreflightReadSurvival(unittest.TestCase):
         self.assertIn("task mismatch", str(ctx.exception))
 
     def test_capability_consumed_after_mutation_gate(self):
+        # Use reconciler/close_pr so this purity-order test does not require a
+        # branches/ worktree (author create_issue would hit #274/#683 guards).
+        # Test isolation stays explicit; production author guards remain live
+        # under force-on (see tests/test_issue_683_workflow_scope_guards.py).
         mcp_server.record_preflight_check("whoami")
         mcp_server.record_preflight_check(
-            "capability", resolved_role="author", resolved_task="create_issue"
+            "capability", resolved_role="reconciler", resolved_task="close_pr"
         )
-        mcp_server.verify_preflight_purity(task="create_issue")
+        mcp_server.verify_preflight_purity(task="close_pr")
         with self.assertRaises(RuntimeError) as ctx:
-            mcp_server.verify_preflight_purity(task="create_issue")
+            mcp_server.verify_preflight_purity(task="close_pr")
         self.assertIn("has not been resolved", str(ctx.exception))
 
     def test_whoami_recovery_after_violation_clears_capability(self):