feat(userscript): scroll or reposition from the widened tap strip

touch-action is resolved at gesture start, so the strip cannot be both
browser-scrolled and script-dragged. Own the gesture and split by intent:
a swipe from the strip scrolls the page, a ~400ms hold arms a reposition
drag, and the visible sliver still drags with no hold. Adds the missing
pointercancel reset.

userscript/manga-bookmark.user.js

@@ -904,6 +904,7 @@
   const FAB_KEY = "mangabm:fabpos";
   const FAB_MARGIN = 12; // vertical breathing room at the top and bottom
   const FAB_EDGE = 0;    // horizontal: an edge tab sits flush against the side
+  const ARM_MS = 400;    // hold this long on the invisible strip to arm a drag
 
   function clamp(v, lo, hi) {
     return Math.max(lo, Math.min(hi, v));
@@ -947,23 +948,69 @@
     applyFabPos(fab, side, y);
   }
 
+  // A gesture that starts on the visible sliver drags immediately, as it always
+  // has. A gesture that starts on the invisible #hit strip scrolls the page
+  // instead — unless it is held for ARM_MS first, which arms a reposition drag.
+  // ponytail: the scroll is hand-rolled (no momentum/fling) and assumes the
+  // document is the scroller. That is the price of touch-action:none, which we
+  // need so a hold can claim pixels a swipe would otherwise scroll. If the
+  // stiffness annoys, give #hit touch-action:pan-y and accept that vertical
+  // repositioning must start on the 7px sliver.
   function makeDraggable(fab) {
-    let down = false, moved = false, sx = 0, sy = 0, offX = 0, offY = 0;
+    let down = false, moved = false, armed = false, scrolling = false, fromHit = false;
+    let sx = 0, sy = 0, offX = 0, offY = 0, lastY = 0, armTimer = 0;
+
+    function reset() {
+      down = moved = armed = scrolling = fromHit = false;
+      clearTimeout(armTimer);
+      fab.classList.remove("armed");
+      fab.style.transition = "";
+    }
+
+    function scrollPage(e) {
+      e.preventDefault();
+      window.scrollBy(0, lastY - e.clientY);
+      lastY = e.clientY;
+    }
+
     fab.addEventListener("pointerdown", (e) => {
+      delete fab.dataset.dragged; // stale flag would swallow this gesture's click
       down = true;
       moved = false;
+      armed = false;
+      scrolling = false;
+      fromHit = e.target.id === "hit";
       sx = e.clientX;
       sy = e.clientY;
+      lastY = e.clientY;
       const r = fab.getBoundingClientRect();
       offX = e.clientX - r.left;
       offY = e.clientY - r.top;
       fab.setPointerCapture(e.pointerId);
       fab.style.transition = "none";
+      clearTimeout(armTimer);
+      armTimer = setTimeout(() => {
+        armed = true;
+        fab.classList.add("armed"); // visible confirmation the hold took
+      }, ARM_MS);
     });
+
     fab.addEventListener("pointermove", (e) => {
       if (!down) return;
-      if (!moved && (Math.abs(e.clientX - sx) > 6 || Math.abs(e.clientY - sy) > 6)) moved = true;
-      if (!moved) return;
+      if (scrolling) {
+        scrollPage(e);
+        return;
+      }
+      if (!moved) {
+        if (Math.abs(e.clientX - sx) <= 6 && Math.abs(e.clientY - sy) <= 6) return;
+        clearTimeout(armTimer);
+        if (fromHit && !armed) {
+          scrolling = true;
+          scrollPage(e);
+          return;
+        }
+        moved = true;
+      }
       e.preventDefault();
       const w = fab.offsetWidth, h = fab.offsetHeight;
       fab.style.left = clamp(e.clientX - offX, 0, window.innerWidth - w) + "px";
@@ -971,11 +1018,16 @@
       fab.style.top = clamp(e.clientY - offY, 0, window.innerHeight - h) + "px";
       fab.style.bottom = "auto";
     });
+
     fab.addEventListener("pointerup", (e) => {
       if (!down) return;
-      down = false;
-      fab.style.transition = "";
-      if (!moved) return; // tap — let the click handler toggle the panel
+      const didDrag = moved, didScroll = scrolling;
+      reset();
+      if (didScroll) {
+        fab.dataset.dragged = "1"; // suppress any click trailing the scroll
+        return;
+      }
+      if (!didDrag) return; // tap — let the click handler toggle the panel
       fab.dataset.dragged = "1"; // suppress the click that trails this drag
       const w = fab.offsetWidth, h = fab.offsetHeight;
       const r = fab.getBoundingClientRect();
@@ -985,6 +1037,8 @@
       applyFabPos(fab, side, y);
       saveFabPos(side, y / window.innerHeight);
     });
+
+    fab.addEventListener("pointercancel", reset);
   }
 
   // ============================================================