[daniele21]

Homepage typography consistency

• Uses canonical Plus Jakarta Sans for headings and Inter for body across Hero, DECIDE, BUILD, TEST, MEASURE and ABOUT. Technical mono labels remain intentionally distinct.
• Stage titles and their mobile 320–760px responsive sizes now share the exact same CSS tokens, weights (800), line-height, tracking and section intro sizing. Hero keeps its larger display hierarchy.
• Standardized card/feature title sizes and converted ad hoc 450/650/760/820/860-style weights into role tokens 400/500/600/700/800 that are actually loaded.
• Extended Google Fonts request to load Inter 700 and 800, avoiding browser-synthesized bold. Supports existing light/dark modes.
• Added source-level contracts for canonical typography and Playwright computed-font audits for all stage headings, ABOUT, Hero and cards across 320/390/768/1440px in light/dark, without changing experiment data or carousel behavior.

Validation

• ✅ Build, unit tests and smoke tests passed.
• ✅ Homepage visual browser capture passed, including new computed-style font and size checks.
• ⏳ Broader visual workflow continues running separately on project routes, which were not changed by this PR.

Merge directly into dev per user request; main unchanged.