Replace the rewrite requirement check with a BodyResponseModifier
marker and treat header and body modifiers separately.
This ensures header/status rewrites still apply when body rewriting is
blocked (for binary, encoded, or chunked responses), while body changes
are skipped safely. It also avoids body reset/close side effects and
returns early on passthrough responses.
Update middleware tests to cover split header/body behavior and themed
middleware body-skip scenarios.
35d54194c0