Brummel
a6a314bb98
Add an additive, fluent GraphBuilder authoring surface that wires a blueprint's topology by typed node handles and port/field names instead of raw positional indices. Node references are Copy NodeHandle values (a node reference cannot be mistyped); only port/field names are strings, resolved against each node's cached NodeSchema by exactly-one-match at a single fallible build() -> Result<Composite, BuildError> — the Binder posture, one level up. build() lowers to the unchanged Composite::new, so the compilat stays index-wired (C23): names resolve at the authoring boundary and never reach FlatGraph. A new From<Composite> for BlueprintNode lets add() accept nested composites. Verified: builder-authored sma_cross is structurally equal to the hand-wired fixture, and the full builder-authored harness lowers to a byte-identical FlatGraph (equal edges + sources). The five BuildError variants (Unknown/Ambiguous In/Out, BadHandle) are covered, and the SimBroker exposure/price legs are now addressable by name (the #21 legibility win). The structural close of the exposure/price swap (#21) is deliberately out of scope — this builder makes the swap legible, not impossible — tracked as #65. Two plan-test corrections applied during implementation (both in-scope, no behaviour change): the harness parity test uses compile_with_params with a topology-invariant param vector on both sides (the harness declares three params, so a no-param compile() would trip ParamArity), and the error asserts use .err()/Some(...) rather than unwrap_err() (Composite is not Debug). aura-engine 123 tests green (+9); full workspace green; clippy --all-targets -D warnings clean. Existing index-form Composite::new sites and tests untouched (coexistence). closes #64