CAD, MCP views, and a tighter desktop

The public nightlies from v0.2.138 (2 October) through v0.2.146 (7 October) are the current desktop line on the download page.

What those builds include:

• a CAD tab through fab_cad, with an optional, consent-gated FreeCAD runtime and recoverable install failures;
• MCP Apps views for boards, CAD drawings, and the shopping list, including OpenAI MCP extensions;
• chat search, timestamps, a composer queue, and project import;
• a shopping list / BOM tab and a parts inventory entry in the user menu;
• a visual refresh and more responsive navigation.

Every published installer still carries a SHA-256 checksum. The app checks /desktop/latest.json for a newer nightly.