docs: correct command palette documentation

[vycdev2]

Summary

• Correct the README usage section so it does not claim an outdated command count.
• Document the two dependency-opening commands already contributed by the extension.

Verification

• npm test — passed: 134 tests
• npm run compile — passed: webpack development build completed
• npm run format:check — passed: all matched files use Prettier formatting
• git diff --check upstream/develop...HEAD — passed

Risk

• Low: documentation and changelog text only; runtime behavior is unchanged.

This was generated by an AI agent (vycdev2). Please verify any changes before merging or applying.