Add documentation claim-language check and trim README

[prayagv]

Summary

• Add a documentation workflow that rejects workstation-only links and unqualified superlatives, matching the check used elsewhere in the organization.
• Move the npm command reference and fixture/design-notes detail out of the README into docs/commands.md and docs/writing-tests.md, linked from both the intro and the documentation index.

Test plan

• All local markdown links verified to resolve after the moves.
• Local grep confirms no banned self-assessment terms in tracked markdown.