The built-in sample that `aura graph` renders and `aura sweep` runs is now a
"trend + momentum, weighted blend" strategy that exercises four authoring/viewer
capabilities the single-level sample left dark:
- multiply-nested composites: root -> signals -> {trend = sma_cross, momentum = macd};
- a multi-param node inside a composite: blend = LinComb(3) (weights[0]/[1] shown);
- a multi-output node: momentum (the macd composite) re-exports macd/signal/histogram,
two of which the blend consumes;
- bind(): blend.weights[2] is fixed as a structural constant, so it drops out of the
sweepable param surface (and renders absent).
The new `signals` composite reuses the existing sma_cross/macd builders unchanged; the
sweep re-paths its axes to the eight free params (still a 4-point grid) and runs an
18-tick warm-up stream (showcase_prices) so the MACD EMA-of-EMA chain and the all-Any
LinComb join warm up. The render fixture (sample-model.json) is re-captured, and a new
headless guard (viewer_nested_depth) pins that the viewer renders the nesting to depth 2
with valid Graphviz ids. Pure authoring over already-shipped primitives — no engine or
graph-viewer.js change.
The flat run_sample, run_macd/macd(), the inline model_golden test, and the viewer are
untouched. A third sweep-param pin in tests/cli_run.rs (the aura sweep E2E) was re-pathed
in lockstep with its in-crate twin.
closes#62
