perf(cuesheet): revert lazy-autosize (Exp B) — metrics show it regresses

Measured baseline vs lazy-autosize at CPU 4x (median of 3, ~1140 row mounts):
- cell.autosize eliminated (15.2s -> 0) BUT
- EventRow.mount avg +39% (179 -> 248ms), longtask +32%, longFrames 201->219,
  and per-row re-renders ~2x (getVisibleCells renders 4648 -> 8902).
Deferring autosize destabilises virtuoso row-height measurement (rows=1
textareas), causing more re-render churn, and collapses note display.
Net negative — not merged. Keeping instrumented baseline.

apps/client/src/common/components/input/auto-textarea/AutoTextarea.tsx

@@ -1,6 +1,6 @@
 // @ts-expect-error no types from library
 import autosize from 'autosize/dist/autosize';
-import { FocusEvent, RefObject, useCallback, useEffect } from 'react';
+import { RefObject, useEffect } from 'react';
 
 import { timeSync } from '../../../devtools/cuesheet-metrics/usePerfMark'; // PERF-METRICS
 import Textarea, { type TextareaProps } from '../textarea/Textarea';
@@ -10,41 +10,18 @@ interface AutoTextAreaProps extends TextareaProps {
 }
 
 /**
- * A textarea that automatically resizes based on its content.
- *
- * `autosize()` forces a synchronous reflow (reads scrollHeight) and installs a MutationObserver.
- * Doing that on mount makes it expensive when many of these are mounted at once (e.g. virtualised
- * table rows during scroll), so we only attach autosize while the field is focused for editing and
- * keep it in sync with the value during that time.
+ * A textarea that automatically resizes based on its content
  */
-export function AutoTextarea({ value, inputref, onFocus, onBlur, ...textAreaProps }: AutoTextAreaProps) {
-  const handleFocus = useCallback(
-    (event: FocusEvent<HTMLTextAreaElement>) => {
-      timeSync('cell.autosize', () => autosize(inputref.current)); // PERF-METRICS
-      onFocus?.(event);
-    },
-    [inputref, onFocus],
-  );
-
-  const handleBlur = useCallback(
-    (event: FocusEvent<HTMLTextAreaElement>) => {
-      if (inputref.current) {
-        autosize.destroy(inputref.current);
-      }
-      onBlur?.(event);
-    },
-    [inputref, onBlur],
-  );
-
-  // while focused, keep the height in sync as the value changes
+export function AutoTextarea({ value, inputref, ...textAreaProps }: AutoTextAreaProps) {
+  // when the value changes, we use the ref to reapply autosize
   useEffect(() => {
     const node = inputref.current;
-    if (node && document.activeElement === node) {
-      autosize(node);
-    }
+    timeSync('cell.autosize', () => autosize(inputref.current)); // PERF-METRICS
+
+    return () => {
+      autosize.destroy(node);
+    };
   }, [inputref, value]);
 
-  return (
-    <Textarea ref={inputref} value={value} onFocus={handleFocus} onBlur={handleBlur} {...textAreaProps} />
-  );
+  return <Textarea ref={inputref} value={value} {...textAreaProps} />;
 }