v1.19.0: faster startup

Signed by Mozilla for Firefox 140 or later, plus an unpacked build for Chrome, Edge and Brave.

Firefox: click markdown-pr-sentence-comments-1.19.0.xpi below and allow github.com to install the add-on.

Chrome, Edge, Brave: download markdown-pr-sentence-comments-chrome-1.19.0.zip, unzip it to a folder you keep, open chrome://extensions, switch on Developer mode, and click Load unpacked. For an update, replace the folder contents and click the reload icon.

Faster in this version:

• The mount sweep stops as soon as every Markdown file has mounted, instead of always scrolling the whole page with a pause per step, and the second sweep is gone: the toggles are clicked where they are.
• Only one startup runs at a time, and the page watcher ignores our own changes while rendering. Before, every click queued another full startup.
• The OpenSpec files and the glossary load in parallel with rendering, so the Spec outline is ready when the panel appears.
• The glossary only scans blocks it has not seen yet.
• The console prints a timing line for each phase, which helps if something is still slow.

Based on chienyuanchang/rich-diff-comments (MIT).