Add AnswerLens to llms.txt directory

[ciihom]

Adds AnswerLens to the llms.txt directory.

Checks:

• https://app.sfdj.net/llms.txt returns 200 with text/plain; charset=utf-8.
• python3 -m json.tool src/data/llms-txt.json passes.
• npm run lint passes with existing warnings, no errors.

Note: AnswerLens does not publish llms-full.txt, so this entry only uses the current llms.txt.