Improve README hero section for developer conversion #153

Summary

Refresh the top of the README so new visitors immediately understand what StructKit is, why it is different, and how to try it in under a minute.

Why this matters

Most GitHub traffic decides whether to star, try, or leave from the first screen of the README. StructKit has strong differentiators, but the README should make the value proposition and quickstart impossible to miss.

Scope

• Add a sharper one-line value proposition near the top.
• Add a concise “who this is for” section: DevEx/platform teams, DevOps engineers, AI coding workflow users, and solo developers.
• Move or tighten the Cookiecutter/Copier comparison so the differentiators are visible earlier.
• Add a 60-second quickstart block with install + one useful generation command.
• Add clear CTAs: try a template, star the repo, open a discussion, contribute examples.
• Include or link to a short demo GIF/video.

Acceptance criteria

• The first screen answers: what it is, who it is for, why it is different, and how to try it.
• Quickstart commands are tested and accurate.
• README includes at least one visual demo or a placeholder path for one.
• README links to examples, docs, discussions, and contribution guidance.