Server-side coverage for the critical-CSS shim (PR #36024 salvage):
- user theme → style block emitted with ONLY real bundle variable names
(--background-base/--midground-base from layerVars(),
--theme-font-sans/--theme-base-size from typographyVars()/index.css),
and an html,body rule expressed via those vars so runtime theme
switches never leave a stale canvas/font
- built-in / unknown / non-string active theme → no block
- malformed theme YAML and load_config() exceptions → no crash, index
still serves
- </style> breakout attempt in a theme value stays escaped
- mount_spa integration: block present in <head> for user themes,
absent for built-ins
558fcb6146