Markdown preview scroll sync broken after #287050 merged to main

[AshtonYoon]

A problem occurred where #287050 did not work properly after being merged into main.

Bug 1: Editor jumps when scrolling the preview

File: src/preview/preview.ts

The merge retained this.#isScrolling = false inside the early-return guard of scrollTo(), which the original PR intentionally removed. This resets the timer-based flag on the first call, allowing subsequent editor scroll events to re-trigger forward sync during reverse sync — causing the editor to jump.

 if (this.#isScrolling) {
-    this.#isScrolling = false;   // ← should have been removed
     return;
 }

Bug 2: Preview → editor sync doesn't work until editor is scrolled once

File: preview-src/index.ts

The PR switched onUpdateView to a timer-based reset (scrollDisabledCount = 0 after 50ms), but left initialization and resize handlers still using scrollDisabledCount += 1 with no timer reset. Since the scroll handler no longer decrements the counter, scrollDisabledCount stays at 1 after page load and blocks all preview-to-editor sync indefinitely.

Repro:

1. Open a markdown file + preview side-by-side
2. Scroll the preview → editor does not follow
3. Scroll the editor once, then scroll the preview → now it works

Fix: Apply the same timer-reset pattern to initialization and resize handlers. PR to follow.