feat(cli): surface the composite doc in the graph viewer (#125)

The viewer threads the model's doc through normalizeModel into both
composite view states — appended to INFO.B (collapsed box) and INFO.C
(expanded cluster frame) — and shows the root composite's doc as a muted
header line (#rootdoc span in GRAPH_HEAD, empty when absent; the DOM
population sits in the browser-only block, the same boundary as the
breadcrumb). viewer_tooltip.mjs pins the doc'd cases beside the
byte-exact un-doc'd pins; sample-model.json gains the additive doc key;
e2e drives aura graph over a nested-doc blueprint into the emitted page.

closes #125

crates/aura-cli/tests/graph_construct.rs

@@ -1040,6 +1040,37 @@ fn graph_doc_field_moves_content_id_but_not_identity_id() {
     );
 }
 
+/// Property (#125 viewer/#3, nested-composite doc through the real render
+/// pipeline): the sibling test above only proves a ROOT-level `doc` reaches
+/// the rendered page — the viewer threads a composite's doc onto its own
+/// tooltip (INFO.B/INFO.C in graph-viewer.js), which needs the doc present on
+/// a NESTED composite def, not just the root. `aura graph <file>` over a
+/// blueprint whose one node is a nested composite carrying `doc` must embed
+/// that exact string in the emitted page's `composites` section of
+/// `window.AURA_MODEL` — the composite-def half of `graph_model.rs`'s
+/// `doc_fragment`, exercised through the actual file-load -> render CLI
+/// binary, not just the library function called directly.
+#[test]
+fn graph_render_embeds_a_nested_composites_doc() {
+    let out = std::process::Command::new(BIN)
+        .arg("graph")
+        .arg(fixture("nested_doc_blueprint.json"))
+        .output()
+        .expect("spawn aura graph <blueprint>");
+    assert_eq!(
+        out.status.code(),
+        Some(0),
+        "render exit: {:?}\nstderr: {}",
+        out.status,
+        String::from_utf8_lossy(&out.stderr)
+    );
+    let html = String::from_utf8(out.stdout).expect("utf-8 stdout");
+    assert!(
+        html.contains(r#","doc":"momentum leg: change over a lookback, gated by the trend sign""#),
+        "rendered page does not embed the nested composite's doc: {html}"
+    );
+}
+
 /// The `gang` op's arity refusal (fewer than two members) reads as prose at the
 /// binary seam, attributed to its op index, never the raw `GangArity` Debug name.
 #[test]