fix(editor): reflow scroll containers after paste to refresh click hit-testing (#146)

Pasting markdown/code inserts React NodeViews that mount asynchronously; until
the next reflow the browser's hit-test geometry is stale, so ProseMirror's
posAtCoords/caretRangeFromPoint maps a click to the wrong (offset) line — which
users reported clears itself on any scroll. Reproduce that scroll's side effect
with a ZERO-delta nudge (re-assign scrollTop/scrollLeft to their current value)
on every scrollable ancestor + the document scrolling element, run across two
animation frames so it lands after the pasted content + NodeViews commit. The
nudge does not move the viewport.

Wired into editor-paste-handler's handlePaste, which ProseMirror's someProp runs
(as an editorProps handler) before the MarkdownClipboard plugin that performs the
markdown/code insert — so the nudge is scheduled on exactly the paste path that
triggers the bug. Complements the structural NodeViewContent-order fix in this
branch.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/client/src/features/editor/components/common/editor-paste-handler.tsx

@@ -22,12 +22,75 @@ const ATTACHMENT_NODE_TYPES = [
 
 const ATTACHMENT_URL_RE = /\/api\/files\/([0-9a-f-]+)\//;
 
+const SCROLLABLE_OVERFLOW = new Set(["auto", "scroll", "overlay"]);
+
+/**
+ * Collect every scrollable ancestor of the editor DOM whose hit-test layer
+ * could be stale after a paste, plus the document scrolling element. We nudge
+ * ALL of them (a zero-delta nudge is harmless) because the real scroll container
+ * varies — a styled overflow ancestor on most pages, the document itself on
+ * others — and `overflow: overlay` (common on macOS, where #146 reproduces)
+ * must count as scrollable too. Called only AFTER the paste has committed, so
+ * `scrollHeight > clientHeight` reflects the inserted content.
+ */
+function collectScrollAncestors(node: HTMLElement): HTMLElement[] {
+  const targets: HTMLElement[] = [];
+  // Walk every ancestor (incl. body/html) — on some layouts the scroll lives on
+  // body rather than the documentElement that scrollingElement points at.
+  let el: HTMLElement | null = node.parentElement;
+  while (el) {
+    const { overflowX, overflowY } = getComputedStyle(el);
+    const scrollsY =
+      SCROLLABLE_OVERFLOW.has(overflowY) && el.scrollHeight > el.clientHeight;
+    const scrollsX =
+      SCROLLABLE_OVERFLOW.has(overflowX) && el.scrollWidth > el.clientWidth;
+    if (scrollsY || scrollsX) targets.push(el);
+    el = el.parentElement;
+  }
+  const docEl = document.scrollingElement as HTMLElement | null;
+  if (docEl && !targets.includes(docEl)) targets.push(docEl);
+  return targets;
+}
+
+/**
+ * Re-flow the editor's scroll containers after a paste so the browser refreshes
+ * its click hit-testing geometry (#146). Pasting markdown/code inserts React
+ * NodeViews that mount ASYNCHRONOUSLY; until the next reflow, ProseMirror's
+ * posAtCoords/caretRangeFromPoint can map a click to a stale (offset) line —
+ * which users observed clears itself on any scroll. We reproduce that scroll's
+ * side effect with a ZERO-delta nudge (re-assign scrollTop/Left to their current
+ * value), invalidating the hit-test layer WITHOUT moving the viewport. The
+ * container lookup AND the nudge run across two animation frames so they happen
+ * AFTER the pasted content + NodeViews commit (only then is the real scroll
+ * container measurable).
+ */
+function reflowAfterPaste(editor: Editor) {
+  const dom = editor.view.dom as HTMLElement;
+  requestAnimationFrame(() => {
+    requestAnimationFrame(() => {
+      for (const el of collectScrollAncestors(dom)) {
+        // Capture into locals first so this reads as a scroll nudge, not a
+        // no-op self-assignment (which lint would flag), while still poking the
+        // scroll position to refresh hit-testing.
+        const { scrollTop, scrollLeft } = el;
+        el.scrollTop = scrollTop;
+        el.scrollLeft = scrollLeft;
+      }
+    });
+  });
+}
+
 export const handlePaste = (
   editor: Editor,
   event: ClipboardEvent,
   pageId: string,
   creatorId?: string,
 ) => {
+  // Schedule a post-paste reflow for every paste path: the pasted content (and
+  // its async NodeViews) settles after this handler returns, so we nudge on the
+  // next frames to keep click hit-testing aligned (#146).
+  reflowAfterPaste(editor);
+
   const clipboardData = event.clipboardData.getData("text/plain");
 
   if (INTERNAL_LINK_REGEX.test(clipboardData)) {