Refactor external tools organization and add file search API endpoint

🤖 Generated with [OpenCode](https://opencode.ai)

Co-Authored-By: OpenCode <noreply@opencode.ai>

packages/opencode/src/util/lazy.ts

@@ -0,0 +1,11 @@
+export function lazy<T>(fn: () => T) {
+  let value: T | undefined
+  let loaded = false
+
+  return (): T => {
+    if (loaded) return value as T
+    value = fn()
+    return value as T
+  }
+}
+