The default vector store path was hardcoded to /tmp/{provider}, which fails in:
- macOS LaunchAgents: /tmp cleared on reboot, limited permissions
- Linux systemd: may have noexec restrictions or private /tmp namespaces
- Windows: /tmp does not exist
- Docker: /tmp is ephemeral unless mounted as a volume
Replace with a cross-platform user data directory:
- Linux/macOS: $XDG_DATA_HOME or ~/.local/share/mem0/{provider}
- Windows: %APPDATA%/mem0/{provider}
This follows the XDG Base Directory Specification on Linux and the
conventional APPDATA path on Windows, making mem0 work reliably in
all deployment environments without requiring explicit path config.
Closes#4279
