docs: fix TypeScript unrecoverable error example

[P-r-e-m-i-u-m]

Summary

• Replace the TypeScript unrecoverable error example with the documented retryPresets.noRetry pattern.
• Note that the TypeScript SDK does not currently expose a public unrecoverable error type.
• Update the best-practices wording to describe disabling retries for non-retryable failures.

Fixes #173.

Testing

• git diff --check
• python scripts/vendor_mermaid.py --check
• python scripts/vendor_glightbox.py --check
• python -m zensical build --clean

[yaythomas]

thank you very much for excellent contribution @P-r-e-m-i-u-m