New address and a way to report problems

No change to how the check works; this release is about where Crossweft lives and how to tell us when it gets something wrong.

• New address: the repository moved to github.com/AnastasiyaW/crossweft. GitHub redirects the old one. Install commands, plugin manifests, the marketplace entry and the docs use the new address.
• Feedback: issue forms for a problem, an idea and an agent report. When Crossweft itself gets something wrong, the skill tells the agent to draft a short report for its user, without private code, and to let the user decide whether to send it.
• README: header and how-it-works images, a release badge that follows the latest release, and a link to this project page.
• GitHub Action: a Marketplace-ready name, Crossweft seam check.

For new installs, use the new address.