Add counter example; fix configuration

examples/accident-counter/src/counter.tsx

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+import React, { useReducer, useEffect } from 'react';
+import { reducer } from './reducer';
+
+export const Counter = () => {
+  const [state, dispatch] = useReducer(reducer, { count: 0 });
+  const unit = state.count === 1 ? 'day' : 'days';
+
+  useEffect(() => {
+    window.document.title = `${state.count} ${unit}`;
+  }, [state.count]);
+
+  return (
+    <div className="p-8 space-y-8 text-center bg-white border rounded-md shadow-lg border-slate-400">
+      <div className="space-y-4">
+        <div data-test-id="counter-count" className="font-semibold text-8xl">
+          {state.count}
+        </div>
+        <p>
+          <span data-test-id="counter-unit">{unit}</span> since the last
+          accident.
+        </p>
+      </div>
+      <div className="flex gap-4">
+        <button onClick={() => dispatch({ type: 'increment' })}>
+          Increment
+        </button>
+        <button
+          onClick={() => dispatch({ type: 'decrement' })}
+          disabled={state.count === 0}
+        >
+          Decrement
+        </button>
+        <button
+          onClick={() => dispatch({ type: 'reset' })}
+          disabled={state.count === 0}
+        >
+          Reset
+        </button>
+      </div>
+    </div>
+  );
+};

examples/accident-counter/src/reducer.test.js

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+import { describe, it, expect } from 'vitest';
+import { reducer } from './reducer';
+
+describe('reducer', () => {
+  it('should return the initial state', () => {
+    const initialState = { count: 0 };
+    expect(reducer()).toEqual(initialState);
+  });
+
+  it('should handle decrement action', () => {
+    const initialState = { count: 0 };
+    const action = { type: 'increment' };
+    const expectedState = { count: 1 };
+    expect(reducer(initialState, action)).toEqual(expectedState);
+  });
+
+  it('should handle increment action', () => {
+    const initialState = { count: 1 };
+    const action = { type: 'decrement' };
+    const expectedState = { count: 0 };
+    expect(reducer(initialState, action)).toEqual(expectedState);
+  });
+
+  it('should handle unknown action', () => {
+    const initialState = { count: 0 };
+    const action = { type: 'UNKNOWN' };
+    expect(reducer(initialState, action)).toEqual(initialState);
+  });
+});

examples/accident-counter/src/reducer.ts

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+type CounterState = {
+  count: number;
+};
+
+type CounterAction =
+  | { type: 'increment' }
+  | { type: 'decrement' }
+  | { type: 'reset' };
+
+export function reducer(
+  state: CounterState = { count: 0 },
+  action: CounterAction,
+): CounterState {
+  if (!action) return state;
+
+  switch (action.type) {
+    case 'increment':
+      return { count: state.count + 1 };
+    case 'decrement':
+      if (state.count > 0) {
+        return { count: state.count - 1 };
+      }
+      return { count: 0 };
+    case 'reset':
+      return { count: 0 };
+    default:
+      return state;
+  }
+}