[dajiaohuang]

Summary

• Reject empty and whitespace-only tool names in the catalog renderer, matching the nonblank-name requirement in CONTRIBUTING.md.
• Clarify the existing 50-byte UTF-8 limit in the validation error.
• Add a regression test through the normal entry-validation path.

Validation

• git diff --check passed.
• Rust/Cargo are not installed in this environment, so the Rust test suite was not run.
• CI was not queried or awaited.