fix(docs): publish production files at bucket root

[Si40Code]

Summary

• publish production docs at the OSS bucket root currently served by docs.heycall-e.com
• keep optional prefixes available for explicitly configured non-production origins
• compare the public index and OpenAPI byte-for-byte with the built artifact so stale content fails the workflow

API contract

Not changed.

Validation

• pnpm run validate
• 7 deployment-script tests passed
• 25 Playwright tests passed
• production dry run planned 97 files at the bucket root

Checklist

• I kept the change focused and public-facing.
• I removed secrets, private URLs, phone numbers, and customer data.
• Any OpenAPI change describes behavior supported by the public API.
• I updated tests when observable site behavior changed.
• Screenshots are not applicable to this deployment-only fix.
• I ran pnpm run validate.