fix(nodes): resolve ComfyUI placeholders anywhere in the node input

Inside a loop the engine hands a node the loop context rather than the
upstream node's output, so a plain input.data lookup misses the values a
graph needs. Placeholder resolution now searches the input tree, matching
what the code nodes in this workflow already have to do.

nodes/ai/comfyui-prompt.js

@@ -157,13 +157,36 @@ function findPlaceholders(text) {
     return found;
 }
 
+// Inside a loop the engine hands a node the loop item rather than the upstream
+// node's output, and the upstream result is nested somewhere under it. Resolve a
+// path against the obvious roots first, then search the tree for it.
+function deepResolve(root, path, depth) {
+    if (!root || typeof root !== 'object' || depth > 6) {
+        return undefined;
+    }
+
+    const direct = getPath(root, path);
+    if (direct !== undefined) {
+        return direct;
+    }
+
+    const keys = Object.keys(root);
+    for (let i = 0; i < keys.length; i++) {
+        const found = deepResolve(root[keys[i]], path, depth + 1);
+        if (found !== undefined) {
+            return found;
+        }
+    }
+    return undefined;
+}
+
 function substitute(template, data) {
     let out = String(template);
     const keys = findPlaceholders(out);
 
     for (let i = 0; i < keys.length; i++) {
         const key = keys[i];
-        let value = getPath(data, key);
+        let value = deepResolve(data, key, 0);
 
         if (value === undefined && key === 'seed') {
             value = Math.floor(Math.random() * 1000000000000000);
@@ -311,7 +334,9 @@ module.exports = {
             throw new Error('A ComfyUI workflow graph is required');
         }
 
-        const data = input && input.data !== undefined ? input.data : input;
+        // Resolve against the whole input: the upstream result may be nested under
+        // the loop item rather than sitting at input.data.
+        const data = input;
         const base = String(config.baseUrl).replace(/\/+$/, '');
         const attempts = 1 + (Number(config.retryCount) > 0 ? Number(config.retryCount) : 0);