fix registrar writebacks and own the State Hub access map

Ignore generated WORK-RECORDS.md/.custodian-brief.md in the registrar git
precondition, commit identifier writebacks even when registration is
incomplete, and name the remaining records in the error. Add
config/state-hub-access.yaml as the single source for the AGENTS.md port
map, rendered by rmgr scaffold and refreshed with --refresh-hub-access.

Assistant: grok
Assistant-Session: 01a04996-76e8-7f53-b971-1885cfbed436

tests/test_scaffold.py

@@ -75,3 +75,5 @@ def test_cli_scaffold(tmp_path: Path):
         == 0
     )
     assert (dest / "INTENT.md").is_file()
+    agents = (dest / "AGENTS.md").read_text(encoding="utf-8")
+    assert "10.43.68.154:8000" in agents