Proposal for inline LLM instructions in HTML based on llms.txt

Introduces a new convention, `<script type="text/llms.txt">`, for embedding LLM instructions directly within HTML responses. This convention leverages the browser's behavior of ignoring unknown script types to embed LLM-specific content without affecting regular rendering. The proposal is based on the `llms.txt` standard and aims to provide agents with in-band instructions on how to access protected resources, such as Vercel preview deployments, by referencing available MCP server functions or bypass token mechanisms.