Add Rust domain kernel and wire contracts

crates/remora-contracts/tests/golden.rs

@@ -0,0 +1,87 @@
+use remora_contracts::{AttemptOutcomeRequestDto, EventFrameDto, JobFailureDto, JobSubmissionDto};
+use serde::Deserialize;
+use serde_json::Value;
+
+#[derive(Deserialize)]
+struct Corpus {
+    job_submissions: Vec<Value>,
+    event_frames: Vec<Value>,
+    attempt_outcomes: Vec<Value>,
+    job_failures: Vec<Value>,
+}
+
+#[test]
+fn mutable_dtos_round_trip_the_shared_corpus() {
+    let corpus: Corpus =
+        serde_json::from_str(include_str!("../../../contracts/golden/domain.json")).unwrap();
+    for value in corpus.job_submissions {
+        let dto: JobSubmissionDto = serde_json::from_value(value.clone()).unwrap();
+        assert_eq!(serde_json::to_value(dto).unwrap(), value);
+    }
+    for value in corpus.event_frames {
+        let dto: EventFrameDto = serde_json::from_value(value.clone()).unwrap();
+        assert_eq!(serde_json::to_value(dto).unwrap(), value);
+    }
+    for value in corpus.attempt_outcomes {
+        let dto: AttemptOutcomeRequestDto = serde_json::from_value(value.clone()).unwrap();
+        assert_eq!(serde_json::to_value(dto).unwrap(), value);
+    }
+    for value in corpus.job_failures {
+        let dto: JobFailureDto = serde_json::from_value(value.clone()).unwrap();
+        assert_eq!(serde_json::to_value(dto).unwrap(), value);
+    }
+}
+
+#[test]
+fn dto_bindings_reject_cross_field_and_nullability_violations() {
+    let contradictory_failures = [
+        serde_json::json!({
+            "class": "source_not_found",
+            "message": "missing",
+            "retryable": true
+        }),
+        serde_json::json!({
+            "class": "transient_target",
+            "message": "unavailable",
+            "retryable": false
+        }),
+    ];
+    for value in contradictory_failures {
+        assert!(serde_json::from_value::<JobFailureDto>(value).is_err());
+    }
+
+    let null_optional = serde_json::json!({
+        "source": {
+            "kind": "http",
+            "url": "https://example.invalid/file",
+            "result_path": "file.bin"
+        },
+        "label": null
+    });
+    assert!(serde_json::from_value::<JobSubmissionDto>(null_optional).is_err());
+}
+
+#[test]
+fn websocket_bindings_reject_values_outside_the_schema() {
+    let invalid = [
+        serde_json::json!({
+            "schema_version": 2,
+            "kind": "heartbeat",
+            "event_id": "event_0001",
+            "sequence": 1,
+            "cursor": "cursor-value-0001",
+            "occurred_at": "2026-07-15T00:00:00Z"
+        }),
+        serde_json::json!({
+            "schema_version": 1,
+            "kind": "heartbeat",
+            "event_id": "event_0001",
+            "sequence": 0,
+            "cursor": "short",
+            "occurred_at": "not-a-date"
+        }),
+    ];
+    for value in invalid {
+        assert!(serde_json::from_value::<EventFrameDto>(value).is_err());
+    }
+}