Function encode_composite_chain 

pub fn encode_composite_chain<E: CompositeEncoder>(
    enc: &E,
    rec: &E::Rec,
    args: &E::Args,
    text_calls: &[TextDrawCall],
) -> Result<(), String>

The composite + text orchestration, previously hand-duplicated in each backend’s encode_composite_and_text. An error mid-text propagates without closing the pass, matching the prior DX/VK behaviour (the frame fails either way: the target is just left mis-stated). This is unused on Metal, where a render encoder must be endEncoding-ed before the command buffer commits: skipping end_composite on a text error would crash at commit, so Metal’s encode_composite_and_text ends the encoder on any ? with a ScopedEncoder RAII guard instead.