Validate one glyph's markup against the geometry allowlist. Returns the serialized clean markup, or null with reasons when ANY part is disallowed: rejection over silent stripping, so a hostile glyph cannot launder itself into a partial render.
Validate one glyph's markup against the geometry allowlist. Returns the serialized clean markup, or null with reasons when ANY part is disallowed: rejection over silent stripping, so a hostile glyph cannot launder itself into a partial render.