* fix(frontend): address mobile workspace polish blockers
* fix(frontend): prevent mobile landing overflow
* fix(frontend): keep landing sections within mobile viewport
Section titles used a fixed text-5xl with no word breaking, and the
<section> flex items had default min-width:auto, so wider Linux font
metrics in CI pushed content past the viewport (scrollWidth 345 > 320).
Make titles/subtitles responsive with break-words, constrain section
width with min-w-0, and add an overflow-x-clip guard on the page root.
* fix(frontend): address review feedback on mobile landing PR
- add hamburger Sheet nav below sm: so mobile users keep docs/blog access
- switch useIsMobile to useSyncExternalStore to avoid hydration swap flash
- memoize artifactContent so it isn't rebuilt on every streamed token
- use slot-based key in HeroWordRotate; drop flex-wrap so SuperAgent never orphans at 320px
- delete unused word-rotate.tsx dead code
- move section gutter to <main> for a uniform mobile padding contract
- harden e2e: per-viewport overflow tests, locale-stable artifact selector, focus-ring asserts light vs dark differ
---------
Co-authored-by: Willem Jiang <willem.jiang@gmail.com>
