docs: move GoBarryGo users to ProtoPeek Downloader

[shreyam1008]

Summary

• replace the public GoBarryGo landing page with a human-readable compatibility page for ProtoPeek v0.5 Downloader
• preserve every GoBarryGo v0.0.9 legacy download and document the reversible migration path
• freeze superseded GoBarryGo roadmap/package-submission work without deleting history or artifacts
• fix generated JSON-LD and strengthen the static Pages verification contract

Activation boundary

This PR activates only the compatibility page. It does not create a domain redirect, change DNS or Pages settings, archive the repository, remove releases, or alter package registries.

Verification

• PUBLIC_SITE_URL=https://gobarrygo.shreyam1008.com.np PUBLIC_BASE_PATH=/ bun run verify
• PUBLIC_SITE_URL=https://shreyam1008.github.io PUBLIC_BASE_PATH=/gobarrygo/ bun run verify
• go test ./tests
• jq -e . product.json docs/screenshots.json
• git diff --check

After merge and successful Pages deployment, the runbook status will receive a separate dated evidence update.