Rename md-to-pdf.html to index.html for GitHub Pages

[Copilot]

Enables GitHub Pages hosting by renaming the main HTML file to index.html, which is automatically served as the site root.

Changes

• Renamed md-to-pdf.html → index.html

[Copilot]

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[evanlow]

@copilot Can you review this html file for correctness?

[Copilot]

@copilot Can you review this html file for correctness?

I reviewed index.html for this PR. The change is a pure filename rename (md-to-pdf.html → index.html) with no content edits, and there are no remaining references to the old filename in the repo. For GitHub Pages, this is correct and should serve the app at the site root as intended.