Add borda.html: stateless ranked-choice voting tool

[Quidge]

Summary

A single-file Borda-count ranked-choice voting tool for small groups.

• Organizer opens the tool, enters a title + 2-12 choices + expected voter count, and gets a shareable URL. The entire election is packed into the URL fragment — nothing is stored on a server.
• Voters open the link, type their name, rank the choices with up/down arrow buttons (simpler and more reliable than drag-and-drop on mobile), and copy the resulting short ballot string to send back.
• Anyone can open the same link, flip to the Tally tab, paste all ballots, and see the Borda count result. Rejected ballots come with a human-readable reason; ties share a rank (standard competition ranking).

Designed mobile-first: large tap targets, 16px inputs to avoid iOS zoom-on-focus, system font stack, no external assets. URL-fragment encoding uses base64url with SHA-256 checksum derivation via Web Crypto.

Screenshots

Desktop — create a poll, generate a shareable link:

Mobile — vote and generate a ballot string:

Desktop — tally view with Borda-count results:

Mobile — tally view:

Test plan

Manually tested end-to-end via Playwright (uv run python -m http.server + Playwright driving Chromium at desktop 900×700 and mobile 390×780 viewports):

• Create mode: fill title + 3 choices + voter count, generate share URL with #e= fragment
• Vote mode (mobile): rename, reorder with up/down arrows, generate ballot string
• Tally mode: paste 3 ballots, see correct Borda count (Thai 4pts, Pizza 3pts, Sushi 2pts)
• Invalid ballots surface with a reason (malformed + checksum mismatch)
• Ties share a rank (two items tied for 1st → next distinct rank is 3rd)
• Mobile layout at 390px wide — large tap targets, no horizontal overflow