fix(test): add missing label field to AnyAgentTool mock in params test

label is a required property on AgentTool; the mock was missing it,
causing a TS error in CI.

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

src/agents/pi-tools.params.test.ts

@@ -22,6 +22,7 @@ describe("assertRequiredParams", () => {
     const tool = wrapToolParamNormalization(
       {
         name: "write",
+        label: "write",
         description: "write a file",
         parameters: {},
         execute: vi.fn(),