docs: update best models plot

[Alezander9]

Updates the BrowserCode best-models radial plot PNGs from benchmark-x-laminar origin/main (64922ea), replacing the older Gemini 3 Flash lowest-cost card with Minimax M3.

Verification:

• Visually inspected light and dark PNGs in static/
• Confirmed diff only touches static/browsercode_best_models_{light,dark}.png

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Summary by cubic

Updates the BrowserCode best-models radial plot and README to reflect the latest benchmark: the lowest-cost model is now minimax-m3, replacing gemini-3-flash-preview.
Updated the light/dark PNGs in static/ and the “Lowest cost” line in README.md.

^{Written for commit 444492a. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 2 files

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