feat(sync): add typed flat patch boundary

req: sync/002

req: sync/003

hemx-js/runtime/hemx.js

@@ -18,6 +18,7 @@
   const sseSources = new WeakMap();
   const atomStores = new WeakMap();
   const dragKeys = new WeakMap();
+  let currentOperationId = null;
   const clientHandlers = new Map();
   const clientRuns = new WeakMap();
 
@@ -253,6 +254,7 @@
     try {
       if (!handler) throw new Error(`unknown client-local hemx handler: ${name}`);
       const stateVersion = Number(root.getAttribute("data-hemx-client-state-version") || "1");
+      const operationId = crypto.randomUUID();
       const wire = await handler(
         1,
         event.type,
@@ -264,7 +266,12 @@
       );
       if (!(wire instanceof Uint8Array)) throw new Error(`client-local hemx handler ${name} returned an invalid effect batch`);
       if (!active()) return;
-      applyBatch(wire, root);
+      currentOperationId = operationId;
+      try {
+        applyBatch(wire, root);
+      } finally {
+        currentOperationId = null;
+      }
       if (name === "reorder_card") {
         const key = dragKeys.get(root) || el.getAttribute("data-card-id");
         const moved = key ? firstElement(root, (node) => node.getAttribute("data-key") === key) : null;
@@ -469,8 +476,18 @@
         if (op.title) document.title = op.title;
       }
     } else if (op.kind === "emit") {
-      handleRuntimeEvent(scope, op.name, op.payload);
-      emit(scope, op.name, op.payload);
+      let payload = op.payload;
+      if (currentOperationId && op.name === "hemx:sync-patch") {
+        const patch = JSON.parse(payload);
+        if (patch.idempotencyKey !== "$hemx-interaction" || patch.operationId !== "$hemx-interaction") {
+          throw new Error("hemx sync patch is missing its interaction identity");
+        }
+        patch.idempotencyKey = currentOperationId;
+        patch.operationId = currentOperationId;
+        payload = JSON.stringify(patch);
+      }
+      handleRuntimeEvent(scope, op.name, payload);
+      emit(scope, op.name, payload);
     }
     return true;
   }