v1.20.0: faster startup, take two

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

Firefox: click markdown-pr-sentence-comments-1.20.0.xpi below and allow github.com to install the add-on.

Chrome, Edge, Brave: download markdown-pr-sentence-comments-chrome-1.20.0.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, measured on a real pull request:

• A console.log inside a check that runs for every button on every sweep step is gone. It printed DOM nodes hundreds of times per startup.
• The files are mounted while the route-data request is still in flight, instead of one after the other.
• Larger sweep steps, shorter pauses.
• The glossary candidates are fetched in parallel instead of three 404s in a row.
• OpenSpec paths that carry nothing, such as .gitkeep, are skipped; each one cost a 200 KB page download.

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