fix(build): tighten TypeScript configuration and update dependencies for zod v4 compatibility

test/test.agent-e2e.ts

@@ -66,6 +66,7 @@ tap.test('agent should call a single tool and incorporate the result', async ()
 
 tap.test('agent should pick the right tool from multiple options', async () => {
   const callLog: string[] = [];
+  type TCalculatorOperation = 'add' | 'subtract' | 'multiply' | 'divide';
 
   const result = await runAgent({
     model,
@@ -79,7 +80,7 @@ tap.test('agent should pick the right tool from multiple options', async () => {
           a: z.number(),
           b: z.number(),
         }),
-        execute: async ({ operation, a, b }: { operation: string; a: number; b: number }) => {
+        execute: async ({ operation, a, b }: { operation: TCalculatorOperation; a: number; b: number }) => {
           callLog.push(`calculator:${operation}(${a}, ${b})`);
           switch (operation) {
             case 'add': return String(a + b);