fix(reader): keep text selection on the current page - #718

Summary

Fix Android WebView text selection moving the paginated reader container toward a neighboring column while users drag native selection handles.

The paginator now:

• cancels and restores partial swipe movement when text selection takes ownership;
• holds the aligned page position against unowned native selection auto-scroll;
• preserves the existing intentional one-second edge-hold page navigation;
• leaves continuous reading mode and its scroll inertia behavior intact.

Validation

• pnpm vitest run packages/app-expo/src/lib/reader/paginator-touch-navigation.test.js — 10 passed
• TZ=UTC pnpm --filter @readany/core test — 584 passed
• pnpm --filter @readany/app-expo test — 24 passed
• pnpm exec tsc --noEmit -p packages/app-expo/tsconfig.json
• pnpm exec biome check packages/foliate-js/paginator-touch.js packages/app-expo/src/lib/reader/paginator-touch-navigation.test.js
• pnpm --filter @readany/app-expo run build:reader
• pnpm --filter app exec vite build
• Physical Android WebView: selection expanded across a multi-column EPUB page in both directions without changing the visible page alignment; reopening the book restored the same saved page.

pnpm --filter app build still stops on upstream main at the pre-existing unused MS_SUPPORTED_LANGS declaration in packages/core/src/translation/providers.ts; this branch does not modify that file, and the direct Vite production bundle passes.