fix(ui): Projection ref params now filter objects by matching type

- RefCombobox infers object_type from param name when not explicitly set
- e.g. param 'agent' automatically shows only agent-type objects
- Also fixed engine type signature to preserve object_type in params

小橘 🍊（NEKO Team）

packages/engine/src/engine.ts

@@ -478,7 +478,7 @@ export async function createProjectionDef(
   db: D1Database,
   name: string,
   sources: Array<{ event_def: string; bindings: Record<string, string>; expression: string }>,
-  params: Record<string, { type: 'ref' }>,
+  params: Record<string, { type: 'ref'; object_type?: string }>,
   valueSchema: { type: string },
   initialValue: any,
 ): Promise<{ name: string; hash: string }> {

packages/engine/ui/src/components/Projections.tsx

@@ -150,6 +150,7 @@ export default function Projections() {
                       objects={objects}
                       objectsByType={objectsByType}
                       objectType={schema.object_type}
+                      paramName={key}
                     />
                   ) : (
                     <input
@@ -232,29 +233,41 @@ function RefCombobox({
   objects,
   objectsByType,
   objectType,
+  paramName,
 }: {
   value: string
   onChange: (v: string) => void
   objects: Array<{ id: string; type: string }>
   objectsByType: Record<string, string[]>
   objectType?: string
+  paramName?: string
 }) {
   const [query, setQuery] = useState('')
 
-  // Filter objects by object_type if specified
+  // Filter objects by object_type if specified, or infer from param name
+  // Convention: param name often matches the object type (e.g. param "agent" → type "agent")
+  const effectiveObjectType = useMemo(() => {
+    if (objectType) return objectType
+    if (paramName) {
+      const types = new Set(objects.map(o => o.type))
+      if (types.has(paramName)) return paramName
+    }
+    return undefined
+  }, [objectType, paramName, objects])
+
   const relevantObjects = useMemo(() => {
-    if (!objectType) return objects
-    return objects.filter((o) => o.type === objectType)
-  }, [objects, objectType])
+    if (!effectiveObjectType) return objects
+    return objects.filter((o) => o.type === effectiveObjectType)
+  }, [objects, effectiveObjectType])
 
   const relevantByType = useMemo(() => {
-    if (!objectType) return objectsByType
+    if (!effectiveObjectType) return objectsByType
     const filtered: Record<string, string[]> = {}
-    if (objectsByType[objectType]) {
-      filtered[objectType] = objectsByType[objectType]
+    if (objectsByType[effectiveObjectType]) {
+      filtered[effectiveObjectType] = objectsByType[effectiveObjectType]
     }
     return filtered
-  }, [objectsByType, objectType])
+  }, [objectsByType, effectiveObjectType])
 
   const filtered = useMemo(() => {
     if (!query) return relevantObjects