feat(0091): byte-canonical blueprint emit; record the equality-surface decision

#164 — tighten the C24 "canonical, versioned" blueprint contract on two corners
the milestone fieldtest surfaced. Both forks were derivable; resolved with
rationale (recorded on #164).

Fork 1 — canonical artifact carries no trailing newline. `blueprint_to_json`
returns the JSON value with no trailing newline (647 bytes for the SMA-cross
fixture); `aura graph build` had framed it with a `println!` (648). The library
serializer is the single canonical source — the form content-addressed topology
identity (#158) hashes — so the CLI is a transport that must not mutate the
bytes: `build_cmd` now `print!`s the canonical bytes verbatim, making the CLI and
library emit paths byte-identical. RED-first: the new E2E
`graph_build_emit_is_byte_canonical_no_trailing_newline` pinned the trailing
newline (FAIL), green after the one-line change. The two cycle-0088 `.out.json`
goldens are re-recorded at 647 bytes. The loader stays lenient (a trailing
newline on input still parses, Tier-1 robustness; the milestone fieldtest's
`mt_4` tolerance check is unaffected).

Fork 2 — the canonical JSON is the blueprint equality/identity surface; no
second in-memory PartialEq/Debug is added. `Composite`/`BlueprintNode` cannot
derive them: `PrimitiveBuilder` (aura-core node.rs) holds a
`build: Box<dyn Fn(&[Cell]) -> Box<dyn Node>>` closure, neither comparable nor
printable. Equality could only be defined over the serialized data, of which
`blueprint_to_json` is already the single source; a separate in-memory equality
notion would be a redundant second source of truth and a drift hazard against
the form #158 hashes. Recorded the decision (discharges acceptance box 2's "or
JSON-string is the intended equality surface" arm) in the C24 ledger; no code
added for it.

Verified: cargo test --workspace green (51 suites, incl. the new RED->green E2E);
cargo clippy --workspace --all-targets -D warnings clean.

closes #164

crates/aura-cli/src/graph_construct.rs

@@ -132,7 +132,11 @@ pub fn build_cmd() {
         std::process::exit(2);
     }
     match build_from_str(&doc) {
-        Ok(json) => println!("{json}"),
+        // `print!`, not `println!`: the canonical artifact is exactly the library
+        // `blueprint_to_json` bytes (the form #158 content-addresses) — a JSON value
+        // with no trailing newline. The CLI is a transport; it must not frame the
+        // canonical bytes (#164).
+        Ok(json) => print!("{json}"),
         Err(msg) => {
             eprintln!("aura: {msg}");
             std::process::exit(2);

crates/aura-cli/tests/graph_construct.rs

@@ -58,6 +58,17 @@ fn graph_build_emits_blueprint_for_a_valid_document() {
     assert!(stdout.contains("\"SMA\""), "carries the nodes: {stdout}");
 }
 
+/// The canonical blueprint artifact carries no trailing newline: `aura graph build`
+/// emits exactly the library `blueprint_to_json` bytes (the form #158 content-addresses),
+/// not a display-framed line. Byte-canonical across the CLI and library surfaces (#164).
+#[test]
+fn graph_build_emit_is_byte_canonical_no_trailing_newline() {
+    let (stdout, _stderr, ok) = run(&["graph", "build"], SIGNAL_DOC);
+    assert!(ok, "exit success");
+    assert!(!stdout.ends_with('\n'), "no trailing newline on the canonical emit: {stdout:?}");
+    assert!(stdout.contains("\"format_version\":1"), "still the #155 envelope: {stdout}");
+}
+
 #[test]
 fn graph_build_fails_fast_at_the_offending_op() {
     let doc = r#"[{"op":"add","type":"SMA","name":"fast"},{"op":"add","type":"Nope"}]"#;

docs/design/INDEX.md

@@ -1870,6 +1870,19 @@ the capitalized `ScalarKind` (`"F64"`). Worked example:
 `aura graph introspect --vocabulary | --node <T> | --unwired`. (Surfacing this same
 grammar in `aura graph build --help` rides with the CLI-discoverability work, #159.)
 
+**Canonical form (#164).** The canonical blueprint artifact is exactly the bytes
+`blueprint_to_json` returns — a JSON value with **no trailing newline**.
+`aura graph build` emits those bytes verbatim (it does not frame them with a display
+newline via `println!`), so the CLI and library emit paths are **byte-identical** — a
+prerequisite for content-addressed topology identity (#158, a hash over the canonical
+form). The **canonical JSON is also the blueprint's equality / identity surface**:
+`Composite` / `PrimitiveBuilder` deliberately carry **no in-memory `PartialEq` /
+`Debug`** (the recipe holds a `build: Box<dyn Fn>` closure — non-comparable,
+non-printable; equality could only be defined over the serialized *data*, of which
+`blueprint_to_json` is already the single source — a second in-memory notion would be
+a drift hazard against the very form #158 content-addresses). The loader stays lenient
+(a trailing newline on input still parses, Tier-1 robustness).
+
 ---
 
 ## Open architectural threads not yet resolved

fieldtests/cycle-0088-construction-op-script/c0088_1_blueprint.out.json

@@ -1 +1 @@
-{"format_version":1,"blueprint":{"name":"graph","nodes":[{"primitive":{"type":"SMA","name":"fast","bound":[{"pos":0,"name":"length","kind":"I64","value":{"I64":2}}]}},{"primitive":{"type":"SMA","name":"slow","bound":[{"pos":0,"name":"length","kind":"I64","value":{"I64":4}}]}},{"primitive":{"type":"Sub","name":"sub"}},{"primitive":{"type":"Bias","name":"bias"}}],"edges":[{"from":0,"to":2,"slot":0,"from_field":0},{"from":1,"to":2,"slot":1,"from_field":0},{"from":2,"to":3,"slot":0,"from_field":0}],"input_roles":[{"name":"price","targets":[{"node":0,"slot":0},{"node":1,"slot":0}],"source":"F64"}],"output":[{"node":3,"field":0,"name":"bias"}]}}
+{"format_version":1,"blueprint":{"name":"graph","nodes":[{"primitive":{"type":"SMA","name":"fast","bound":[{"pos":0,"name":"length","kind":"I64","value":{"I64":2}}]}},{"primitive":{"type":"SMA","name":"slow","bound":[{"pos":0,"name":"length","kind":"I64","value":{"I64":4}}]}},{"primitive":{"type":"Sub","name":"sub"}},{"primitive":{"type":"Bias","name":"bias"}}],"edges":[{"from":0,"to":2,"slot":0,"from_field":0},{"from":1,"to":2,"slot":1,"from_field":0},{"from":2,"to":3,"slot":0,"from_field":0}],"input_roles":[{"name":"price","targets":[{"node":0,"slot":0},{"node":1,"slot":0}],"source":"F64"}],"output":[{"node":3,"field":0,"name":"bias"}]}}

fieldtests/cycle-0088-construction-op-script/c0088_2_blueprint.out.json

@@ -1 +1 @@
-{"format_version":1,"blueprint":{"name":"graph","nodes":[{"primitive":{"type":"SMA","name":"fast","bound":[{"pos":0,"name":"length","kind":"I64","value":{"I64":3}}]}},{"primitive":{"type":"SMA","name":"slow","bound":[{"pos":0,"name":"length","kind":"I64","value":{"I64":8}}]}},{"primitive":{"type":"Sub","name":"sub"}},{"primitive":{"type":"Bias","name":"bias"}}],"edges":[{"from":0,"to":2,"slot":0,"from_field":0},{"from":1,"to":2,"slot":1,"from_field":0},{"from":2,"to":3,"slot":0,"from_field":0}],"input_roles":[{"name":"price","targets":[{"node":0,"slot":0},{"node":1,"slot":0}],"source":"F64"}],"output":[{"node":3,"field":0,"name":"bias"}]}}
+{"format_version":1,"blueprint":{"name":"graph","nodes":[{"primitive":{"type":"SMA","name":"fast","bound":[{"pos":0,"name":"length","kind":"I64","value":{"I64":3}}]}},{"primitive":{"type":"SMA","name":"slow","bound":[{"pos":0,"name":"length","kind":"I64","value":{"I64":8}}]}},{"primitive":{"type":"Sub","name":"sub"}},{"primitive":{"type":"Bias","name":"bias"}}],"edges":[{"from":0,"to":2,"slot":0,"from_field":0},{"from":1,"to":2,"slot":1,"from_field":0},{"from":2,"to":3,"slot":0,"from_field":0}],"input_roles":[{"name":"price","targets":[{"node":0,"slot":0},{"node":1,"slot":0}],"source":"F64"}],"output":[{"node":3,"field":0,"name":"bias"}]}}