v4.18.3

Focus: Font fallback — stop intermittent serif rendering and stabilize Speed Index.

Changes

• 🐛 Fixed a broken body font stack ("Roboto", "Consolas"): Consolas is a monospace absent on most machines (and on PageSpeed's Linux runners), so with no generic family the browser fell through to its default serif — with font-display: optional, throttled first paints intermittently rendered the whole page in a serif whose metrics diverge from Roboto, swinging Speed Index ~1s between runs
• 🎯 The stack is now Roboto → metric-matched sans-serif → generic sans-serif, plus a "Roboto Fallback" @font-face (local Arial / Liberation Sans re-scaled via ascent-override / descent-override / size-adjust to Roboto's line box) so the pre-webfont paint occupies the exact same space as Roboto — no reflow, no font jump, stable Speed Index whether Roboto lands or not
• ✅ Validated with the full test suite and Lighthouse + rendered-page screenshots