docs: restate PocketJS as a portable application runtime

[doodlewind]

Positioning

One sentence now defines the project everywhere it is stated:

PocketJS is a portable application runtime that turns modern component code into native pixels across radically different hardware.

Surface	Before	After
Landing headline (site/home.html)	"A very ambitious UI runtime."	"UI runtime for every kind of computer"
Landing hero paragraph	"a UI runtime that keeps JSX, Tailwind and reactive state, then removes every layer below them…"	the positioning sentence, then the same removal + QuickJS-on-Rust mechanism
Homepage meta description (site/build.ts)	same UI-runtime framing	positioning sentence + mechanism
Site-wide meta + JSON-LD (SITE_DESC)	"A compact JavaScript runtime for building UI, games, 3D experiences and AI-native applications…"	positioning sentence + one native tree, no DOM/CSS engine/WebView
Site footer blurb (SITE_FOOTER_DESC)	"compact JavaScript runtime for UI, games, 3D and AI-native software"	portable application runtime, native pixels, compact native core
docs/overview intro	"lets you build … interfaces for Sony PSP and PS Vita hardware"	positioning sentence, then the same compile/render mechanism, targets given as examples
docs/architecture intro	"a JSX UI stack that runs apps on real Sony PSP and PS Vita hardware"	positioning sentence, same one-principle line kept
docs/getting-started scope line	"PSP and PS Vita packages"	"PSP, PS Vita, and the other registered targets"
npm description	"High-performance JSX UI outside the browser…"	positioning sentence + Rust core, build-time Tailwind, 8 MB budget

tests/site-stage.test.ts pins the hero copy, so both assertions were updated with it.

README register

Same chapter order as #325, without the landing voice:

• Plain technical headings: Programming model · Rendering and execution · Performance · Native modules · Hardware support · Applications · Getting started · Ahead-of-time compilation · Repository layout · Building and testing · Documentation.
• Subsections carry the detail (### Frameworks, ### Styling, ### Animation, ### Target admission, ### From component to pixel, ### The frame contract, ### On a Sony PSP, ### On a desktop).
• Third-person prose: "Write components as you already do" → "Three frameworks compile to the same native tree"; "What it asks of the machine" → "Performance"; "Not a roadmap" → "Every entry below has booted the runtime on the real machine".
• Adds a Contents list and a Documentation index table; every measurement, receipt link, image and the yui540 attribution are unchanged.

Verification

• bun run test — 11/11 stages green, 443 tests. (One earlier run had a single non-reproducing unit-stage failure, the known flake on this machine; the clean run is the one reported.)
• bun run site:build — homepage, 18 docs pages, 19 blog posts; built output carries the new descriptions.
• Headless Chrome measurement of the new three-line headline (VT323 loaded, not the fallback): widest line 445 px against 651 px of plate interior at 1600w, fits: true and zero horizontal overflow at 1600 / 1280 / 820 / 390 px. A two-line break would have been 636 px against 651 px, so the three-line break is deliberate.
• README relative paths (28) and every pocketjs.dev docs/blog slug re-checked; TOC anchors match the headings.

Docs and site copy only; no runtime code paths touched.

🤖 Generated with Claude Code