chore: clear the two remaining basedpyright warnings

`uv run basedpyright tests/ src/` reported two warnings in files that
predate this change. The pre-commit hook is file-scoped, so neither was
visible unless the owning file was touched.

- src/vector_store/__init__.py: join the lancedb error message with
  explicit `+` instead of adjacent literals (reportImplicitStringConcatenation).
- tests/test_cache_redaction.py: the test covers a private helper
  deliberately, so annotate the import (reportPrivateUsage).

No behavior change; whole-tree check is now clean.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/vector_store/__init__.py

@@ -207,10 +207,10 @@ def _create_store_by_type(store_type: str) -> VectorStore:
         except ImportError as exc:
             raise RuntimeError(
                 "VECTOR_STORE.TYPE is set to 'lancedb', but the 'lancedb' package "
-                "is not installed (for example on macOS Intel, where it is omitted "
-                "from dependencies because PyPI has no wheel). "
-                "Use TYPE 'pgvector' or 'turbopuffer', or install lancedb manually. "
-                f"Original import error: {exc}"
+                + "is not installed (for example on macOS Intel, where it is omitted "
+                + "from dependencies because PyPI has no wheel). "
+                + "Use TYPE 'pgvector' or 'turbopuffer', or install lancedb manually. "
+                + f"Original import error: {exc}"
             ) from exc
 
         return LanceDBVectorStore()

tests/test_cache_redaction.py

@@ -2,7 +2,7 @@
 
 import pytest
 
-from src.cache.client import _redact_cache_url
+from src.cache.client import _redact_cache_url  # pyright: ignore[reportPrivateUsage]
 
 
 class TestRedactCacheUrl: