fix: skip valkey-glide on Windows (#2333)

Skip the unsupported valkey-glide dependency on Windows while preserving automatic installation on supported platforms. Keep missing-client runtime and test paths safe, and update the Valkey integration documentation.

src/langbot/pkg/vector/vdbs/valkey_search.py

@@ -119,7 +119,8 @@ class ValkeySearchVectorDatabase(VectorDatabase):
     def __init__(self, ap: app.Application):
         if not VALKEY_SEARCH_AVAILABLE:
             raise ImportError(
-                "valkey-glide is not installed. Install it with: pip install 'valkey-glide>=2.4.1,<3.0.0'"
+                'valkey-glide is not installed or is unavailable on this platform. '
+                "On Linux or macOS, install it with: pip install 'valkey-glide>=2.4.1,<3.0.0'"
             )
 
         self.ap = ap