fix(web-design-guidelines): bundle pinned guidelines instead of fetching from main

Closes #348

Problem

The skill fetched its rules at runtime from web-interface-guidelines/main/command.md. That file is mutable, so any change to it silently changes what every agent using the skill does, and the skill has no rules if the fetch fails.

Fix

• Bundled command.md in references/command.md, pinned to upstream commit 434b7f91364665f2f733b310ec54809bf8f37937
• SKILL.md now reads the bundled file and tells the agent not to fetch rules from the network
• Added the source URL and SHA-256 (d246b026…0234) so anyone can verify the snapshot
• Added an "Updating the Guidelines" section for refreshing the snapshot
• Explained that $ARGUMENTS in the file means the files the user asked to review
• Bumped version to 1.1.0
• Regenerated web-design-guidelines.zip, which still contained the old fetch-from-main version

Testing

• node scripts/build-discovery-index.mjs passes; the skill now publishes as a .tar.gz that includes references/command.md
• command.md matches upstream at the pinned commit (same SHA-256)

Note

writing-guidelines has the same problem, tracked in #357.