fix(tool): ignore invalid custom tool exports

packages/opencode/src/tool/registry.ts

@@ -201,7 +201,8 @@ export const layer: Layer.Layer<
           // `match` is an absolute filesystem path from `Glob.scanSync(..., { absolute: true })`.
           // Import it as `file://` so Node on Windows accepts the dynamic import.
           const mod = yield* Effect.promise(() => import(pathToFileURL(match).href))
-          for (const [id, def] of Object.entries<ToolDefinition>(mod)) {
+          for (const [id, def] of Object.entries(mod)) {
+            if (!isPluginTool(def)) continue
             custom.push(fromPlugin(id === "default" ? namespace : `${namespace}_${id}`, def))
           }
         }
@@ -396,6 +397,10 @@ function isZodType(value: unknown): value is z.ZodType {
   return typeof value === "object" && value !== null && "_zod" in value
 }
 
+function isPluginTool(value: unknown): value is ToolDefinition {
+  return typeof value === "object" && value !== null && "args" in value && "description" in value && "execute" in value
+}
+
 function isJsonSchemaDefinition(value: unknown): value is JSONSchema7Definition {
   return typeof value === "boolean" || (typeof value === "object" && value !== null && !Array.isArray(value))
 }