test: satisfy pyright strict annotations on the new supervise RPC tests

Add parameter/return annotations to the fake resolver's propose_supervise /
poll_supervise, annotate the test helpers and the shared _ARGS payload, and
narrow the None-able poll result — no behavior change. pylint 9.83, pyright
clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/unit/test_policy_resolver.py

@@ -144,6 +144,7 @@ class TestPolicyResolver(unittest.TestCase):
             {"status": "approved", "notes": "ok", "final_file": None})
         ) as m:
             result = self.r.poll_supervise("10.243.0.7", "tok", "p-7")
+        assert result is not None
         self.assertEqual("approved", result["status"])
         req = m.call_args.args[0]
         self.assertTrue(req.full_url.endswith("/supervise/poll"))