feat(reader): touch selection handles, copy fallback, highlight tap editing

- Custom drag handles (start/end) for post-lift selection adjustment:
  the native handles are disabled with the rest of the native touch
  selection controller; these are positioned at the selection's
  boundary carets and driven through the same clamped caret mapping
- Copy button falls back to execCommand via a transient textarea on
  plain HTTP (navigator.clipboard is unavailable on LAN addresses);
  both paths clear the selection and dismiss the popover
- Only dismiss the selection popover on actual position changes in
  relocate (detail.section is a fresh object on every relocate, so
  reference comparison always saw a move); a tap's no-op relocate
  was closing the just-opened highlight edit popover
- Pin foliate-js f872a01 (synthetic click dispatch on quick taps)
  and 422e8e0 (don't snap taps that never panned)

web/static/input.css

@@ -1434,3 +1434,34 @@
     }
   }
 }
+
+/* Touch selection handles (custom gesture — the native ones are disabled) */
+#selection-handles {
+  position: fixed;
+  inset: 0;
+  pointer-events: none;
+  z-index: 55;
+}
+#selection-handles .sel-handle {
+  position: absolute;
+  top: 0;
+  left: 0;
+  width: 12px;
+  height: 24px;
+  pointer-events: auto;
+  touch-action: none;
+  background: #8ab4f8;
+  border-radius: 6px;
+  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.45);
+  opacity: 0.95;
+}
+#selection-handles .sel-handle::before {
+  content: "";
+  position: absolute;
+  top: -4px;
+  left: 50%;
+  width: 2px;
+  height: 5px;
+  background: inherit;
+  transform: translateX(-50%);
+}