Same decisions, rationale, rejected alternatives and known issues, said with
less padding: ~5,530 -> ~4,730 words (-15%). Every fact from the first draft is
kept; only the wording, duplicated lead-ins and restated context are cut.
Category files under development/ replace the decision prose that was
scattered through README.md and CONTRIBUTING.md. Each decision is a block with
Decision (YYYY-MM) / Why / Rejected / Known issue; the new library.md records
the public API contract and its limitations. AGENTS.md and backlog.tasks now
point at the new home.