WSG STAR batch 2: unused-bytes coverage, no-JS smoke, minification check

[mgifford]

Size: M. Completes the crawl-automatable STAR techniques (batch 1 landed 2026-07-05):

• JS/CSS unused-bytes via Playwright coverage API (remove-redundancy; informs code-splitting) — per-bundle unused %, trended in history.json
• No-JS smoke pass (progressive-enhancement): javaScriptEnabled:false over anonymous pages; assert primary content renders
• Minification heuristic (minified-code): fetch same-origin js/css, flag whitespace ratio above threshold

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Scoped in TOOLING-ROADMAP.md — sized to complete in one AI session. Drafted with AI assistance (Claude Code); no external code copied.