fix(herdr): support Herdr 0.8.0 pane allocation, agent prompt, and length limits

tests/test_herdr_shim_contract.py

@@ -39,7 +39,7 @@ def test_h1_to_h8_shim_contract(mam_sandbox, mock_herdr, mock_agents):
     agent_start_calls = [c for c in calls if len(c) > 1 and c[0] == "agent" and c[1] == "start"]
     assert len(agent_start_calls) > 0
 
-    whitelist = {"--cwd", "--workspace", "--tab", "--split", "--env", "--focus", "--no-focus"}
+    whitelist = {"--cwd", "--workspace", "--tab", "--split", "--env", "--focus", "--no-focus", "--kind", "--pane", "--timeout"}
     for call in agent_start_calls:
         try:
             dd_idx = call.index("--")