refactor(zod): use zod/v4 subpath import for version compatibility

Switch all zod imports from 'zod' and 'zod/mini' to 'zod/v4' subpath.
This enables compatibility with both zod 3.25+ and zod 4.x, as the
subpath import always resolves to the v4 API regardless of the
installed zod version.

- src/feedback.ts: 'zod' → 'zod/v4'
- src/headers.ts: 'zod/mini' → 'zod/v4'
- src/schema.ts: 'zod/mini' → 'zod/v4'
- examples: 'zod' → 'zod/v4'

Author: ryoppippi

examples/claude-agent-sdk-integration.test.ts

@@ -10,7 +10,7 @@
  */
 
 import { tool, createSdkMcpServer } from '@anthropic-ai/claude-agent-sdk';
-import { z } from 'zod';
+import { z } from 'zod/v4';
 import { StackOneToolSet } from '../src';
 
 describe('claude-agent-sdk-integration example e2e', () => {

examples/claude-agent-sdk-integration.ts

@@ -8,7 +8,7 @@
 import assert from 'node:assert';
 import process from 'node:process';
 import { query, tool, createSdkMcpServer } from '@anthropic-ai/claude-agent-sdk';
-import { z } from 'zod';
+import { z } from 'zod/v4';
 import { StackOneToolSet } from '@stackone/ai';
 
 const apiKey = process.env.STACKONE_API_KEY;

examples/tanstack-ai-integration.ts

@@ -10,7 +10,7 @@ import assert from 'node:assert';
 import process from 'node:process';
 import { chat } from '@tanstack/ai';
 import { openai } from '@tanstack/ai-openai';
-import { z } from 'zod';
+import { z } from 'zod/v4';
 import { StackOneToolSet } from '@stackone/ai';
 
 const apiKey = process.env.STACKONE_API_KEY;

src/feedback.ts

@@ -1,4 +1,4 @@
-import { z } from 'zod';
+import { z } from 'zod/v4';
 import { DEFAULT_BASE_URL } from './consts';
 import { BaseTool } from './tool';
 import type { ExecuteConfig, ExecuteOptions, JsonObject, JsonValue, ToolParameters } from './types';

src/headers.ts

@@ -1,4 +1,4 @@
-import { z } from 'zod/mini';
+import { z } from 'zod/v4';
 import type { JsonObject } from './types';
 
 /**

src/schema.ts

@@ -1,4 +1,4 @@
-import { z } from 'zod/mini';
+import { z } from 'zod/v4';
 import { stackOneHeadersSchema } from './headers';
 
 /**