fix(#1427): disable ChromaDB telemetry for sovereignty

ChromaDB enables anonymous telemetry by default, leaking usage
patterns to Chroma Inc. This violates local-first sovereignty.

Two layers of protection:
1. Set ANONYMIZED_TELEMETRY=false env var at import time
2. Pass Settings(anonymized_telemetry=False) to PersistentClient

Closes #1427

nexus/mempalace/searcher.py

@@ -46,7 +46,9 @@ class MemPalaceResult:
 def _get_client(palace_path: Path):
     """Return a ChromaDB persistent client, or raise MemPalaceUnavailable."""
     try:
-        import chromadb  # type: ignore
+        import os
+os.environ["ANONYMIZED_TELEMETRY"] = "false"
+import chromadb  # type: ignore
     except ImportError as exc:
         raise MemPalaceUnavailable(
             "ChromaDB is not installed. "
@@ -59,7 +61,11 @@ def _get_client(palace_path: Path):
             "Run 'mempalace mine' to initialise the palace."
         )
 
-    return chromadb.PersistentClient(path=str(palace_path))
+    import chromadb.config
+    return chromadb.PersistentClient(
+        path=str(palace_path),
+        settings=chromadb.config.Settings(anonymized_telemetry=False),
+    )
 
 
 def search_memories(