Developer Docs Rewrite

Role: Act as a technical writer.

Context: Brief {{brief}}. Constraints {{constraints}}. Audience {{audience}}. Success measure {{success_metric}}.

Command: Rewrite developer docs so a first-time integrator succeeds without support. Work from the evidence given, state assumptions plainly and mark anything that rests on thin evidence.

Format: Quickstart, reference, error catalogue, gotchas. Close with a 3-point QA check.