fix(optimize): remove Font Cache Rebuild that corrupted font rendering

opt_font_cache_rebuild ran `sudo atsutil databases -remove`, which wipes
the macOS ATS font database. Running GUI apps (Codex and browsers) keep
stale font references and render emoji/special glyphs as tofu boxes until
the cache rebuilds, which in practice needs a logout/restart. The guard
only skipped a hardcoded browser list, so Electron apps like Codex were
never covered, and a no-restart batch `mo optimize` left apps broken.

macOS auto-manages font caches and the legitimate rebuild needs a restart
that optimize cannot guarantee, so drop the task outright (same shape as
the Dock Refresh fix in d8220644) along with its helper, registration,
whitelist entry, and tests.