Prompt for create-chkit examples and reorganize docs

[KeKs0r]

Summary

• prompt for bundled create-chkit examples from examples/manifest.json instead of silently defaulting
• add manifest validation/copying for create-chkit builds
• replace repeated package-manager tabs with reusable command components
• promote ObsessionDB docs into a dedicated section

Verification

• bun run check:examples
• bun run --cwd packages/create-chkit typecheck