feat(engine+cli): topology-identity hash — --identity-id beside --content-id

Engine (aura-engine/blueprint_serde): blueprint_to_json factored into
build_doc/serialize_doc (byte-preserving — canonical golden unchanged) and
blueprint_identity_json added: the canonical document with every
non-load-bearing debug symbol (C23) blanked (composite name, instance
names, bound-param names, role names, output re-export names) while
everything load-bearing survives (type ids, node order, edges, role
targets/order, output pairs/order, bound pos/kind/value — openness stays
identity-bearing). Re-exported from lib.rs. Six property tests: renamed
twins (equal identity, unequal canonical), open-vs-bound, bound-value,
edge-swap, nested-composite interior names, role/output renames — the
last two are additive beyond the plan and cover the recursion and
role/output arms the planned four did not.

CLI (aura-cli): graph introspect gains --identity-id, a sibling of
--content-id through the same shared content_id SHA-256 primitive;
composite_from_str factored out of build_from_str (fault strings
byte-identical). The exactly-one introspect dispatch is DELIBERATELY
relaxed: the two id flags form one group and may combine — one build,
both ids, one per line, content id first. In-crate cross-path twin test
(Rust sma_signal vs op-script twin: distinct content ids, one identity
id) beside the existing cross-surface pins; four e2e tests incl. the
previously uncovered count!=1 usage exit-2 path.

topology_hash, the blueprint store, reproduce, and every --content-id
byte stay untouched (spec acceptance 3; all existing pins green).

Verification: cargo build clean; cargo test --workspace 884 passed /
0 failed (873 baseline + 11 new); clippy -D warnings clean; doc build
0 warnings. The implement-loop's Task-4 spec-compliance block was a
plan-byte count mismatch only (plan under-counted pre-existing
blueprint_serde tests 6-vs-7 and did not anticipate the two
sibling-accepted extra tests); gates re-run by hand, all green.

closes #171, refs #180

crates/aura-cli/src/main.rs

@@ -3817,6 +3817,9 @@ struct GraphIntrospectCmd {
     /// Print the graph's content id (topology hash).
     #[arg(long)]
     content_id: bool,
+    /// Print the graph's topology-identity id (debug names stripped).
+    #[arg(long)]
+    identity_id: bool,
 }
 
 #[derive(Args)]
@@ -6015,6 +6018,50 @@ mod tests {
         assert_eq!(topology_hash(&sig), content_id(&blueprint_to_json(&sig).expect("serializes")));
     }
 
+    /// The op-script twin of `sma_signal(Some(2), Some(4))`: same topology —
+    /// SMA(2)/SMA(4) over one `price` role, spread, Bias with `scale` BOUND to
+    /// 0.5 (= `R_SMA_BIAS_SCALE`; boundness is identity-bearing) — differing
+    /// only in debug names (composite "graph" vs "sma_signal", unnamed Bias vs
+    /// `.named("bias")`).
+    const IDENTITY_TWIN_DOC: &str = r#"[
+        {"op":"source","role":"price","kind":"F64"},
+        {"op":"add","type":"SMA","name":"fast","bind":{"length":{"I64":2}}},
+        {"op":"add","type":"SMA","name":"slow","bind":{"length":{"I64":4}}},
+        {"op":"add","type":"Sub"},
+        {"op":"add","type":"Bias","bind":{"scale":{"F64":0.5}}},
+        {"op":"feed","role":"price","into":["fast.series","slow.series"]},
+        {"op":"connect","from":"fast.value","to":"sub.lhs"},
+        {"op":"connect","from":"slow.value","to":"sub.rhs"},
+        {"op":"connect","from":"sub.value","to":"bias.signal"},
+        {"op":"expose","from":"bias.bias","as":"bias"}
+    ]"#;
+
+    /// #171 acc 1 (cross-path identity): the Rust `sma_signal` builder and its
+    /// op-script twin differ in canonical bytes (debug names) — distinct content
+    /// ids — but project to the same identity JSON, hence one identity id across
+    /// authoring paths.
+    #[test]
+    fn identity_id_bridges_the_rust_builder_and_op_script_paths() {
+        let rust_built = sma_signal(Some(2), Some(4));
+        let env = project::Env::std();
+        let json = crate::graph_construct::build_from_str(IDENTITY_TWIN_DOC, &env)
+            .expect("op-script twin builds");
+        assert_ne!(
+            content_id(&json),
+            topology_hash(&rust_built),
+            "authoring paths keep distinct content ids"
+        );
+        let loaded = blueprint_from_json(&json, &|t| std_vocabulary(t)).expect("twin reloads");
+        let identity = |c: &Composite| {
+            content_id(&aura_engine::blueprint_identity_json(c).expect("identity-serializes"))
+        };
+        assert_eq!(
+            identity(&loaded),
+            identity(&rust_built),
+            "one topology -> one identity id across authoring paths"
+        );
+    }
+
     #[test]
     fn mc_r_bootstrap_json_carries_every_bootstrap_field_under_the_mc_r_bootstrap_key() {
         // Property: the `mc_r_bootstrap` output line is the full RBootstrap shape —