[andrewbartels1]

The top demo for the README and the Demos page: SolidWorks' own U-Joint sample, written up as a plain-English prompt and built from it by Claude Code (Opus 5.5, medium effort).

Closes #175. Closes #147, since this demo replaces the bracket demo it asked for.

Built on #210 (the monitor stand), so its first three commits are #210's. Merge #210 first; this PR then shows only the U-joint commits.

What's in it

• The prompt. It was written by reading every part, sketch, feature, dimension and mate of the sample (tests/live/data/ujoint/prompt.md): eight parts, a crank sub-assembly, and a main assembly that must move as a mechanism.
• The replay. tests/live/test_live_sw_ujoint_demo.py opens on the original sample, then replays the session's 294 SolidWorks calls through an in-memory MCP client. Each call is a captioned frame and must end as it did in the session.
• The docs. The README and the Demos page show the original beside the agent's build, the motion GIF (sped up 80 times), the prompt, and a volume table against the sample. Six of the eight parts are within 0.2 %, and all eight within 1 %. The page also says what the agent couldn't do (Tool gaps found building the U-joint: face mates, fixed parts, angled planes, angled chamfers #209).
• The measurement. The same prompt was run in fresh sessions with and without the skill and the server instructions. Both made the same parts. With the skill the agent hit 3 errors against 7 and checked its work twice as often, for about 17 % more tokens. The skill page records both rounds. For Opus 5.5 at medium effort, the skill changed how the agent worked, not what it built, so Skills that improve the agent's results, not just restate the tools #207 tracks writing skills that improve results.
• The queue. The order is now the breaker fix (Circuit breaker locks a tool out after a success and never reopens; add a reset tool #208), support levels (docs(readme): SolidWorks COM API coverage audit + license-tier compatibility tags #79), the U-joint tool gaps (Tool gaps found building the U-joint: face mates, fixed parts, angled planes, angled chamfers #209), then feat(cli): --selftest command and a compatibility-report issue template #179.

Only the motion GIF and the side-by-side JPG are committed. The recording's frames stay local, as .gitignore now requires in every demo folder.