Embedded React: read a ScrollView's offset and scroll range.

Modified from Embedded React (Apache-2.0, Copyright 2026 Cory Lamming) at the
revision pinned in dependencies.lock.json. Changed file: engine/scene/
compositor.c. Proposed upstream as pull request #289.

Adds er_scroll_view_get_offset(node, &x, &y, &max_x, &max_y): the current
offset and the largest offset er_scroll_view_set_offset() accepts on each axis
(content size minus viewport size from the last layout pass, floored at 0). It
returns false for nodes that are not ScrollViews. embeddedReact-scroll-to.patch
declares and calls it from the QuickJS bridge.

diff --git a/engine/scene/compositor.c b/engine/scene/compositor.c
index 95c56fc..b9fe937 100644
--- a/engine/scene/compositor.c
+++ b/engine/scene/compositor.c
@@ -5764,6 +5764,20 @@ void er_tick(uint32_t delta_ms)
     s_now_ms += delta_ms;
 }
 
+bool er_scroll_view_get_offset(const ERNode* node, float* x, float* y, float* max_x, float* max_y)
+{
+    if (!node || (node->type != ER_NODE_SCROLL_VIEW && node->type != ER_NODE_FLAT_LIST))
+        return false;
+
+    const float mx = (float)(node->scroll_content_w - node->computed.w);
+    const float my = (float)(node->scroll_content_h - node->computed.h);
+    *x = node->scroll_offset_x;
+    *y = node->scroll_offset_y;
+    *max_x = mx > 0.0f ? mx : 0.0f;
+    *max_y = my > 0.0f ? my : 0.0f;
+    return true;
+}
+
 void er_scroll_view_set_offset(ERNode* node, float x, float y)
 {
     if (!node || (node->type != ER_NODE_SCROLL_VIEW && node->type != ER_NODE_FLAT_LIST))