feat(aura-cli): aura graph renders a wired graph as an ASCII DAG (#13)

Make a wired graph introspectable so a mis-wiring becomes visible. Two
selectable views, both authored from one built-in sample blueprint:

  aura graph             clustered blueprint view — composites drawn as named
                         ascii-dag cluster boxes (pre-inline, C9)
  aura graph --compiled  flat compilat view — composite boundaries dissolved
                         (C23); the graph the run loop actually runs

The payoff is intrinsic, param-carrying node labels: two SMAs read SMA(2) /
SMA(4), so a swapped fast/slow input reads back differently. This is realized
by a `label()` default method on the core Node trait — a non-load-bearing
render symbol the run loop never reads (wiring is by index), the symbol C23
already reserves citing #13. Recorded as a C8 refinement in the ledger.
Rejected the alternatives in brainstorm: a separate Describe trait (forces a
combined trait-object dance for a label the ledger calls non-load-bearing) and
extrinsic parallel labels (decoupled from the node, so an author can label the
slow SMA "fast" and mask the very bug the render exists to surface).

Mechanism:
- aura-core: Node::label() default method (additive, object-safe, single-line).
- aura-std: per-node overrides — SMA(n)/Exposure(s)/SimBroker(p) carry params;
  Sub/Add/LinComb/Recorder are bare (their identity is not a mis-wiring axis).
- aura-engine: Composite gains an authored `name` (cluster title; dissolves at
  inline) + read-only graph-as-data accessors on Blueprint/Composite. No
  external dependency — the engine stays dependency-pure (C16); ascii-dag lives
  only in aura-cli. The label-free index-wired compilat (C23) is unchanged.
- aura-cli: ascii-dag v0.9.1 + a graph.rs adapter (Vertical mode; labels
  materialized into an owned Vec<String> that outlives the borrow-based Graph).
  `aura run` is untouched (the sample duplication is dedup idea #14).

Tests: a concern-defining test (swapped sample renders != correct), structure
pins (cluster present in blueprint view, absent in compiled view), per-node
label disambiguation, and two frozen byte-goldens of the deterministic render.
The cycle-0012 bit-identical and run-sample non-regression tests stay green.

Verified by the orchestrator (not the agent report): cargo build --workspace
clean; cargo test --workspace all green; cargo clippy --workspace --all-targets
-D warnings clean; both views run live and render as expected.

closes #13

docs/design/INDEX.md

@@ -237,6 +237,14 @@ out-of-graph side effect. In-graph routing stays engine-owned data (the edge tab
 of the graph is the node's own side effect — and that boundary is the
 determinism / graph-as-data boundary (C1/C7).
 
+**Refinement (Construction-layer milestone — render labels, 2026-06-05).** A node
+additionally exposes `label() -> String`, a **single-line, non-load-bearing**
+render symbol: a default trait method the run loop never calls (wiring is by
+index, C23). Overrides carry the node's identifying params (`SMA(2)` vs `SMA(4)`)
+so a graph render (C9 graph-as-data, #13) disambiguates identical node types and
+surfaces a mis-wiring. Like `FieldSpec.name`, it is an informative debug symbol,
+not part of the C8 dataflow contract — adding it changes no run behaviour.
+
 ### C9 — Fractal, acyclic composition
 **Guarantee.** A composite is itself a `Node` that wires a sub-graph and exposes
 one output; signal, combined signal, and (with execution) strategy are all the