Opt out of dark-mode browser extensions (Dark…

Details

The site ships its own dark + light themes; extensions like Dark Reader
re-process the page and break the layout. Declare native theming so they
defer:
- runtime_head.html (shared by v1/v2/v3): add <meta name="darkreader-lock">
  (Dark Reader's official bypass — it skips the page entirely) and
  <meta name="color-scheme" content="dark light"> (tells the browser + well-
  behaved extensions theming is native, so they don't transform it).
- v3 _base.scss: set CSS `color-scheme` per data-theme so the browser's own UI
  (scrollbars, form controls) follows our active theme, not the OS.
No method can force every extension off (they run with user privilege), but
this covers Dark Reader (the dominant one) and the browser natively.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HShRpQUmDUttxD5F89ziDu

Files changed (2)