Translate description truncation clarification to es, fr, zh

[mintlify]

Translates the description truncation behavior clarification from commit 68813a3 to all supported languages (es, fr, zh).

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Note

Low Risk
Documentation-only translation updates; no code or runtime behavior changes.

Overview
Updates the Spanish, French, and Chinese ai/llmstxt.mdx docs to clarify that llms.txt page description values are truncated at 300 characters and at the first newline, while retaining the existing note about additional API spec info from openapi/api frontmatter.

^{Written by Cursor Bugbot for commit 6019b69. This will update automatically on new commits. Configure here.}