Shrink ignores what cannot be seen; blank lines at a block's end go

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

client/js/text_layout.js

@@ -146,3 +146,23 @@ export function layoutText(text, width, size, family) {
     boxHeight: Math.ceil(size * TOP_GAP + lines.length * size * LINE_HEIGHT),
   };
 }
+
+/**
+ * Remove the blank lines at the end of a block's text (Andy, 2026-10-14:
+ * they cannot be seen, and Shrink should keep no room for them) and lay
+ * the block out again.  A text rectangle that is exactly as tall as its
+ * lines, which is what a box grown by typing is, shrinks back to the
+ * lines that remain; one dragged taller than its lines keeps its height,
+ * since that room was asked for.
+ * @param {import('./page_model.js').TextBlock} block
+ * @returns {boolean}  Whether anything changed.
+ */
+export function trimTrailingBlankLines(block) {
+  const trimmed = block.text.replace(/(?:\n[ \t]*)+$/, '');
+  if (trimmed === block.text) return false;
+  const grown = block.height !== null && block.height === Math.ceil(block.boxHeight);
+  block.text = trimmed;
+  Object.assign(block, layoutText(block.text, block.width, block.size, block.font));
+  if (grown) block.height = Math.ceil(block.boxHeight);
+  return true;
+}