Two tasks, CLI-render-only (graph.rs + main.rs tests):
- Task 1: rewrite render_blueprint to the main-graph + where:-definitions model
(composite = opaque node; collect_distinct_composites recursive/deduped by name;
render_definition with [in:k]/[out] port markers); drop ItemDisplay/producer_id/
consumer_ids and the nested-composite unimplemented!; behavioural tests RED->GREEN
(opaque-node, defines-once, nested-no-panic, reuse-defined-once).
- Task 2: recapture the blueprint golden from `aura graph` stdout; full-workspace
test + clippy gate. render_compilat untouched (its golden stays byte-identical).
refs #38
