audit: cycle 0017 (#38) — render_flat dedup + ledger #38 realization note

Architect drift review of the #38 cycle (a70c5fa..cd31447) against the design
ledger. No ledger-contract drift: C23 holds (render_compilat byte-identical,
compiled_view_golden green), C9/C12 honoured (the new main-graph + where:-
definitions view renders a composite as an opaque authoring-level node with its
body defined once — a faithful blueprint/source view vs. the inlined compiled
form), the nested-composite unimplemented! is genuinely removed and tested, and no
orphaned references to the removed ItemDisplay/producer_id/consumer_ids remain in
crates/ (only frozen historical plan docs mention them).

Two debt items, both fixed here (not carried):

- [medium] crates/aura-cli/src/graph.rs — render_compilat open-coded the same
  Graph::with_mode/add_node/add_edge/render idiom the new render_flat helper wraps.
  Fixed: render_compilat now builds its edge-pairs (its Edge structs + source
  targets) and delegates to render_flat, so render_flat is the single flat-build
  point shared by all three render functions. Behaviour-preserving — same node and
  edge insertion order — verified by compiled_view_golden staying byte-identical.

- [low] the retired cluster-box blueprint-render model and its substantive cause
  (ascii-dag 0.9.1's subgraph /2 centering bug; flat-only being the fix) lived only
  in the superseded spec 0013, not in the durable contract layer. Fixed: added a
  "Realization (cycle 0017 — blueprint render = main graph + definitions)" note to
  the ledger (INDEX.md, under the C22 blueprint-view detail) recording the
  opaque-node + where:-definitions model, the authoring-vs-compiled split, the
  ascii-dag-bug rationale, the scale/render-once/nested benefits, and the #37
  playground (enter/focus) counterpart vs. #38 static CLI form.

regression: profile declares no regression scripts and no architect_sweeps — the
architect review is the sole gate. No baseline to update.

Cycle 0017 is drift-clean after these fixes. NOT a milestone close — that needs the
end-to-end milestone fieldtest, still deferred until the sweep root (#32-#33) lands.

crates/aura-cli/src/graph.rs

@@ -137,17 +137,11 @@ pub fn render_compilat(nodes: &[Box<dyn Node>], sources: &[SourceSpec], edges: &
         labels.push(format!("source:{:?}", src.kind));
     }
 
-    let mut g = Graph::with_mode(RenderMode::Vertical);
-    for (id, l) in labels.iter().enumerate() {
-        g.add_node(id, l);
-    }
-    for e in edges {
-        g.add_edge(e.from, e.to, None);
-    }
+    let mut edge_pairs: Vec<(usize, usize)> = edges.iter().map(|e| (e.from, e.to)).collect();
     for (i, src) in sources.iter().enumerate() {
         for t in &src.targets {
-            g.add_edge(source_base + i, t.node, None);
+            edge_pairs.push((source_base + i, t.node));
         }
     }
-    g.render()
+    render_flat(&labels, &edge_pairs)
 }