Make browser tests self-contained and document them (#3767)
t/browser/editicons-rename.js needed a hand-built account and an exported cookie file, so nobody could run it. Add a fixture script that creates and purges its own account and icons, a shared helper that launches Chrome and logs in, and a README with the run command and the rules for new tests. These remain manual checks; CI doesn't run them.
Co-authored-by: Claude Opus 5.5 noreply@anthropic.com
Commit: d43b82b4 Author: Mark Smith