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
Brummel
a6a314bb98