feat(paginator): manual touch scrolling in scrolled layouts — kill the native fling

Scrolled (webtoon) layouts now scroll single-finger drags manually, the
same path paginated layouts always used: the browser's native touch
scrolling — and its fling momentum — is suppressed so the full gesture
stream stays observable to hosts. The reader's chrome UX (bookhoard
handoff item 7) classifies vertical flicks from that stream: flick-down
reveals, down/up dismisses. Side-swipes in paginated layouts and drags
in scrolled ones both page/scroll exactly as before, minus momentum.

Release behavior in scrolled layouts is stop-where-released — no snap,
deliberately: webtoon panels don't align to screen boundaries and a
snap would fight zoomed panning. Long jumps stay the position UI's
job. Pinch zoom, multi-touch, and active touch selection keep their
native behavior via the existing guards (they return before the
preventDefault). Desktop wheel scrolling is untouched.

Version 0.5.4.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "foliate-js",
-  "version": "0.5.3",
+  "version": "0.5.4",
   "description": "Render e-books in the browser",
   "repository": {
     "type": "git",