feat(entity): entity_get_xdata / entity_set_xdata on both engines

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd

discovery/aliases.py

@@ -734,6 +734,14 @@ TOOL_ALIASES: dict[str, ToolAliases] = {
             "hide an entity",
         ),
     ),
+    "entity_get_xdata": ToolAliases(
+        acad=("XDLIST",),
+        synonyms=("extended data", "read xdata", "entity metadata", "registered application data"),
+    ),
+    "entity_set_xdata": ToolAliases(
+        acad=("XDATA",),
+        synonyms=("attach extended data", "write xdata", "tag an entity with metadata"),
+    ),
     "entity_trim": ToolAliases(
         acad=("TRIM", "TR"),
         synonyms=(