Improve purestack cli

[koculu]

Summary

Add CLI version reporting and improve version bumping for the 1.1.7 release.

Changes

• Add purestack --version and -v, reading the installed package version without loading the site generator.
• Document version flags in CLI help and the getting-started guide.
• Support an optional positive integer delta in yarn bump-version, defaulting to 1.
• Cap patch numbers at 99 and carry into the minor number: 1.1.99 → 1.2.0.
• Bump package versions, the exported version, and generator metadata from 1.1.6 to 1.1.7.