docs: replace localhost links in .md copies with production URLs

[Alek99]

Type of change

• Bug fix (non-breaking change which fixes an issue)

Description

This PR fixes RB-047 by replacing broken localhost:3000 links in markdown documentation files (.md copies) with production URLs.

Problem: Documentation pages served as .md files (e.g., https://reflex.dev/docs/getting-started/introduction.md) contained broken localhost:3000 links in their banners. These links were broken for external readers like AI agents, search engine crawlers, and ChatGPT, negatively impacting SEO and AEO (AI Engine Optimization).

Example of the broken banner:

> For AI agents: the complete documentation index is at [llms.txt](https://reflex.dev/docs/llms.txt). 
For a Markdown version, remove the trailing slash from the page URL and append `.md`. 
The docs home is available at [index.md](http://localhost:3000/docs/index.md).

Solution: Changed the markdown directive banner to use hardcoded production URLs (https://reflex.dev/docs/index.md) instead of config-dependent localhost URLs. This is consistent with how PUBLIC_LLMS_TXT_URL is already handled.

Changes:

• Added PUBLIC_DOCS_HOME_MARKDOWN_URL constant pointing to production URL
• Updated _markdown_directive() to use the new constant instead of public_url("/index.md")
• Updated test expectations to match the production URL
• Added news fragment for changelog

Impact

This is a template-level one-line fix that applies to all generated .md documentation files. No individual doc pages were modified.

Testing

• Updated test passes successfully
• Linting passes (ruff check and ruff format)
• Verified no remaining localhost:3000 references in docs generation code
• News fragment added

References

Fixes RB-047

  

[greptile-apps]

Confidence Score: 5/5

[Low impact] The PR appears safe to merge.

Summary

Changes the Markdown banner’s docs-home link to https://reflex.dev/docs/index.md.

• Markdown banners link to the public docs index in every build.

_{Reviews (1) · Last reviewed commit: "Add news fragment for RB-047 fix" · Reviewed by Greptile}

[codspeed]

Merging this PR will not alter performance

⚠️ 20 benchmarks spent significant time in system calls

System calls cannot be consistently instrumented, so they are not included in the measure, which understates the real cost. Please switch to the Walltime instrument to accurately measure system calls.

Measurement and system calls

• test_cli_startup[run_help]
• test_cli_startup[cloud_help]
• test_get_state[disk]
• test_cli_startup[deploy_help]
• test_set_state[disk]
• test_cli_startup[help]
• test_cli_startup[version]
• test_import_cli
• test_event_shutdown_cancel
• test_get_state_uncached[disk]
• …and 10 more

✅ 148 untouched benchmarks

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_{Comparing cursor/fix-docs-md-localhost-links-526f (d572d8f) with main (f10cff4)}