R5: bundle slimming — retarget the budget to the app, no code slimming

Analysed the real dist (gzip + sourcemap attribution): the bundle is already minified + tree-shaken and dominated by the Connect/FlatBuffers transport runtime + generated bindings + the Svelte runtime (~2/3 of main), so no in-scope code slimming is warranted. Lazy-loading was rejected (bundle-size.mjs sums every chunk -> zero total-size win, plus +N gateway fetches of latency); i18n lazy-load and chunk-collapsing likewise (caching/HTTP2).

Instead bundle-size.mjs now measures per HTML entry with three independent gates (app entry <=100 KB, Svelte+i18n shared <=30 KB, landing-own <=5 KB): the app's real payload is its entry chunk + the shared chunk (~97 KB), never landing.js. Same CLI + exit-code contract, CI step unchanged. Fixed the stale ~82 KB figure in the script and ui/README.md. No app code change.

ui/README.md

@@ -21,7 +21,7 @@ pnpm dev          # against a running gateway (Vite proxies /scrabble.edge.v1.Ga
 pnpm check        # svelte-check / tsc
 pnpm test:unit    # Vitest (pure logic + FlatBuffers codec)
 pnpm test:e2e     # Playwright smoke against the mock
-pnpm build        # static bundle into dist/ (prod ~67 KB gzip JS)
+pnpm build        # static bundle into dist/ (prod app ~97 KB gzip JS; per-chunk budget: scripts/bundle-size.mjs)
 pnpm codegen      # regenerate src/gen from edge.proto + scrabble.fbs (dev-time)
 ```