[codex] fix markdown accept negotiation

[basit3407]

What changed

• replaced the boolean markdown check with proper Accept negotiation between text/html and text/markdown
• honor q values and q=0 when ranking supported representations
• return 406 Not Acceptable only when the client rejects both HTML and Markdown
• added regression tests for HTML-preferred requests and unsupported-only Accept headers

Why this changed

The docs site was scoring 75/100 on acceptmarkdown.com because it always served Markdown whenever text/markdown appeared anywhere in the Accept header, even when HTML had a higher preference, and it silently fell back to HTML for unsupported types instead of returning 406.

Impact

• browsers and general clients still default to HTML
• agent clients that explicitly prefer Markdown still receive Markdown
• restrictive unsupported Accept headers now get a standards-correct 406 response instead of a silent HTML fallback

Root cause

The edge middleware only answered ?does this request mention text/markdown with q > 0?? rather than performing best-match content negotiation across the representations the site can actually serve.

Validation

• NODE_PATH=C:\Code\qf-api-docs\node_modules C:\Users\Basit\.cache\codex-runtimes\codex-primary-runtime\dependencies\node\bin\node.exe --test tests\markdown-negotiation.test.cjs
• NODE_PATH=C:\Code\qf-api-docs\node_modules C:\Users\Basit\.cache\codex-runtimes\codex-primary-runtime\dependencies\node\bin\node.exe --test tests\*.test.cjs

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[Copilot]

Pull request overview

Updates the docs edge middleware to perform standards-based Accept content negotiation between HTML and Markdown, ensuring clients receive the best supported representation (or a correct 406 Not Acceptable when none are acceptable).

Changes:

• Replace the previous “mentions text/markdown” boolean check with ranked negotiation honoring q values and wildcards.
• Add a 406 Not Acceptable response path when both HTML and Markdown are rejected.
• Add regression tests covering ranking behavior, HTML-preferred requests, and unsupported-only Accept headers.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/markdown-negotiation-shared.cjs	Adds parsing + ranking helpers for Accept negotiation across supported media types.
src/markdown-negotiation-runtime.cjs	Uses ranked negotiation to choose HTML vs Markdown, and returns 406 when neither is acceptable.
tests/markdown-negotiation.test.cjs	Adds regression tests for ranking, HTML preference via q, and 406 behavior.

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[chatgpt-codex-connector]

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Reviewed commit: e5ecd23c55

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[basit3407]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Chef's kiss.

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".