fix: scope API headers to active provider, temperature falsy bug, template prefix collision

- ControlPanel: only send the active provider's API key header instead of all three
- LLMControls: use nullish coalescing (??) for temperature so 0 is not treated as falsy
- PromptConstructorNode: single-pass regex for @variable resolution to prevent prefix collisions (@foo matching inside @foobar)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/components/nodes/ControlPanel.tsx

@@ -236,9 +236,17 @@ function GenerateImageControls({ node }: { node: Node }) {
     try {
       const capabilities = IMAGE_CAPABILITIES.join(",");
       const headers: HeadersInit = {};
-      if (replicateApiKey) headers["X-Replicate-Key"] = replicateApiKey;
-      if (falApiKey) headers["X-Fal-Key"] = falApiKey;
-      if (kieApiKey) headers["X-Kie-Key"] = kieApiKey;
+      switch (currentProvider) {
+        case "replicate":
+          if (replicateApiKey) headers["X-Replicate-Key"] = replicateApiKey;
+          break;
+        case "fal":
+          if (falApiKey) headers["X-Fal-Key"] = falApiKey;
+          break;
+        case "kie":
+          if (kieApiKey) headers["X-Kie-Key"] = kieApiKey;
+          break;
+      }
 
       const response = await deduplicatedFetch(`/api/models?provider=${currentProvider}&capabilities=${capabilities}`, { headers });
       if (response.ok) {
@@ -832,14 +840,14 @@ function LLMControls({ node }: { node: Node }) {
 
       <div>
         <label className="block text-xs font-medium text-neutral-300 mb-1">
-          Temperature: {nodeData.temperature?.toFixed(2) || "0.70"}
+          Temperature: {(nodeData.temperature ?? 0.7).toFixed(2)}
         </label>
         <input
           type="range"
           min="0"
           max={provider === "anthropic" ? "1" : "2"}
           step="0.01"
-          value={nodeData.temperature || 0.7}
+          value={nodeData.temperature ?? 0.7}
           onChange={handleTemperatureChange}
           className="nodrag nopan w-full h-1 bg-neutral-700 rounded-lg appearance-none cursor-pointer accent-blue-500"
         />

src/components/nodes/PromptConstructorNode.tsx

@@ -119,21 +119,16 @@ export function PromptConstructorNode({ id, data, selected }: NodeProps<PromptCo
     return unresolved;
   }, [localTemplate, availableVariables]);
 
-  // Compute resolved text client-side for preview
+  // Compute resolved text client-side for preview (single-pass to avoid prefix collisions)
   const resolvedPreview = useMemo(() => {
-    let resolved = localTemplate;
-    availableVariables.forEach((v) => {
-      resolved = resolved.replace(new RegExp(`@${v.name}`, 'g'), v.value);
-    });
-    return resolved;
+    const valueMap = new Map(availableVariables.map(v => [v.name, v.value]));
+    return localTemplate.replace(/@(\w+)/g, (match, name) => valueMap.get(name) ?? match);
   }, [localTemplate, availableVariables]);
 
   // Sync resolved text to outputText so downstream nodes can read it before execution
   useEffect(() => {
-    let resolved = nodeData.template;
-    availableVariables.forEach((v) => {
-      resolved = resolved.replace(new RegExp(`@${v.name}`, 'g'), v.value);
-    });
+    const valueMap = new Map(availableVariables.map(v => [v.name, v.value]));
+    const resolved = nodeData.template.replace(/@(\w+)/g, (match, name) => valueMap.get(name) ?? match);
     const outputValue = resolved || null;
     if (outputValue !== nodeData.outputText) {
       updateNodeData(id, { outputText: outputValue });