Add Markdown for Agents limits note

[ask-bonk]

The CI environment doesn't have the right Node version for full validation. The change is straightforward MDX content - a Starlight :::note admonition directive, which is standard syntax used throughout the docs.

Here's a summary of the change:

File: src/content/docs/fundamentals/reference/markdown-for-agents.mdx

Added a :::note admonition in the Limitations section documenting two conditions where Markdown for Agents will not return a converted Markdown response:

1. The origin response does not include a content-length header.
2. The origin response content-length exceeds 1 MB (1,048,576 bytes).

The note also clarifies that in these cases, the original HTML response is returned instead.

Closes #28308

github run

[github-actions]

This pull request requires reviews from CODEOWNERS as it changes files that match the following patterns:

Pattern	Owners
/src/content/docs/fundamentals/	@dcpena, @cloudflare/pcx-technical-writing

[github-actions]

Preview URL: https://79f66ab1.preview.developers.cloudflare.com
Preview Branch URL: https://opencode-issue28308-20260212231426.preview.developers.cloudflare.com

Files with changes (up to 15)

Original Link	Updated Link
https://developers.cloudflare.com/fundamentals/reference/markdown-for-agents/	https://opencode-issue28308-20260212231426.preview.developers.cloudflare.com/fundamentals/reference/markdown-for-agents/

[elithrar]

/bonk revalidate

[ask-bonk]

The preview renders correctly. The note admonition appears properly in the Limitations section with the two bullet points clearly visible.

Validation summary:

• npm run check: 0 errors, 0 warnings (pass)
• Preview deployment: renders correctly, the :::note admonition displays as expected
• Content: the note is well-structured, uses proper MDX syntax, and accurately documents the two conditions (missing content-length header, content-length > 1 MB)
• Style: uses monospace for content-length, provides specific byte value (1,048,576) alongside human-readable "1 MB"

No issues found. This PR is ready to merge.

github run