feat(table-catalog): add external catalog bridge sync (#3569)

Co-authored-by: Henry Guo <marshawcoco@users.noreply.github.com>

scripts/table-catalog/README.md

@@ -179,7 +179,7 @@ current unsupported inventory is:
 - automatic maintenance scheduling: external scheduler hook supported through the worker run endpoint; built-in periodic scheduling is not claimed
 - compaction rewrite: controlled run-once support for unpartitioned Parquet binpack through metadata maintenance; built-in periodic scheduling, sort compaction, delete-file rewrite, and row-level compaction are not claimed
 - row-level delete/update/merge commits: standard catalog commit validates append, overwrite, delete, and replace snapshot manifests for table-warehouse scope, referenced object existence, current-live-file deletes, and stale add/delete conflicts; end-to-end SQL DML client coverage remains a compatibility validation item
-- external catalog bridges: metadata import/register is supported, but Polaris/Glue/DLF/Hive synchronization is unsupported
+- external catalog bridges: metadata import/register and operator-supplied metadata pointer sync are supported for Polaris/Glue/DLF/Hive identity boundaries; online vendor SDK polling and policy mirroring are not claimed
 - multi-table transactions: not a short-term production claim
 
 ## Credential Boundary

scripts/table-catalog/pyiceberg_smoke.py

@@ -166,9 +166,9 @@ UNSUPPORTED_INVENTORY: list[dict[str, str]] = [
     },
     {
         "capability": "external-catalog-bridge",
-        "status": "metadata-import-only",
+        "status": "operator-sync-supported",
         "roadmap_area": "external-catalog",
-        "expected_behavior": "catalog import/register supports an existing Iceberg metadata location, while Polaris, Glue, DLF, and Hive synchronization remain unsupported",
+        "expected_behavior": "catalog import/register and operator-supplied external metadata pointer sync are supported for Polaris, Glue, DLF, and Hive identity boundaries; online vendor SDK polling and policy mirroring are not claimed",
     },
     {
         "capability": "multi-table-transactions",

scripts/table-catalog/test_pyiceberg_smoke.py

@@ -747,6 +747,8 @@ class PyIcebergSmokeConfigTest(unittest.TestCase):
         self.assertIn("background-maintenance-worker", capabilities)
         self.assertIn("external-catalog-bridge", capabilities)
         self.assertIn("multi-table-transactions", capabilities)
+        external_bridge = next(entry for entry in inventory if entry["capability"] == "external-catalog-bridge")
+        self.assertEqual(external_bridge["status"], "operator-sync-supported")
         for entry in inventory:
             self.assertIn("status", entry)
             self.assertIn("roadmap_area", entry)