JLCPCBPartsManager defaulted db_path to a "data/" directory computed
relative to __file__, which fails with read-only filesystems when the
package is installed to a system-managed prefix (e.g. /nix/store, an
immutable container image, or /usr/lib). The same pattern in
download_jlcpcb.py would silently scatter the ~1.5 GB JLCPCB cache
inside the install tree even when it is writable.
The original integration plan (docs/archive/JLCPCB_INTEGRATION_PLAN.md)
called for a per-user database under ~/.kicad-mcp/. This change moves
the default to the platform-appropriate user data directory by adding
a new PlatformHelper.get_data_dir() helper that mirrors the existing
get_config_dir() / get_cache_dir() conventions:
- Linux: XDG_DATA_HOME/kicad-mcp or ~/.local/share/kicad-mcp
- macOS: ~/Library/Application Support/kicad-mcp
- Windows: %USERPROFILE%\.kicad-mcp\data
Both JLCPCBPartsManager and download_jlcpcb.py now resolve their
database paths through this helper. ensure_directories() and
detect_platform() include the new directory. Unit tests parallel to
the existing config_dir/cache_dir cases cover platform-appropriate
paths and the relative-XDG_DATA_HOME edge case.
4e845f24ce