fix: Resolve TypeScript errors after removing slash commands

- Remove third argument from setupClaudeCodeSettings call in index.ts
- Remove unused 'readdir' import from test file

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: km-anthropic

base-action/src/index.ts

@@ -13,7 +13,6 @@ async function run() {
     await setupClaudeCodeSettings(
       process.env.INPUT_SETTINGS,
       undefined, // homeDir
-      process.env.INPUT_EXPERIMENTAL_SLASH_COMMANDS_DIR,
     );
 
     const promptConfig = await preparePrompt({

base-action/test/setup-claude-code-settings.test.ts

@@ -3,7 +3,7 @@
 import { describe, test, expect, beforeEach, afterEach } from "bun:test";
 import { setupClaudeCodeSettings } from "../src/setup-claude-code-settings";
 import { tmpdir } from "os";
-import { mkdir, writeFile, readFile, rm, readdir } from "fs/promises";
+import { mkdir, writeFile, readFile, rm } from "fs/promises";
 import { join } from "path";
 
 const testHomeDir = join(