Covers the composed system channel byte for byte: the context docs and the inlined format specs, the system/user split (unmoved by a user prompt containing the split heading), eco drops proven to really shorten the prompt, vanilla keeping the emit protocols, transparent emptying the channel entirely, and the browser and hands-off additions keeping the signal protocol last.

## Before writing SPEC.md files

Read https://raw.githubusercontent.com/brillout/sdd/refs/heads/main/sdd.md
