fix(mobile): keep scroll mode moving across chapters

[codedogQBY]

Analysis

• [Bug] 翻页问题 #139 reports Android scroll mode cannot move from an intro/description section into the next chapter.
• [Bug] 翻页模式很卡顿；滑动模式在章节处会卡住，无法滑到后面内容。 #361 reports the same chapter-boundary stall in scroll mode, plus perceived paging sluggishness.
• The paginator already supports continuous scrolled rendering, but its touch handler returned early in flow=scrolled. On Android WebView, touch gestures that start inside the iframe do not reliably scroll the shadow-root paginator container, so the reader can dead-end at a section boundary.

Changes

• Add a scrolled-mode touch path in foliate-js/paginator.js that converts iframe touch movement into paginator container scrolling.
• When the user keeps dragging at a scrolled boundary and an adjacent section exists, actively call next()/prev() so the reader advances instead of feeling stuck.
• Preserve the existing paginated swipe/page-turn path unchanged.
• Rebuild packages/app-expo/assets/reader/reader.html so the mobile app loads the updated paginator bundle.

Verification

• pnpm --filter @readany/app-expo run build:reader
• node --check packages/foliate-js/paginator.js
• git diff --check
• pnpm --filter @readany/app-expo exec tsc --noEmit
• Static check that the generated reader.html contains the rebuilt paginator logic

Note: pnpm exec biome check packages/foliate-js/paginator.js is blocked by pre-existing parser/lint diagnostics in that file, including an existing ternary arrow expression near #getRectMapper; this PR did not introduce those diagnostics.

Fixes #361
Fixes #139