sql

Write a single SQL query (PostgreSQL dialect) against the following schema:

```sql
CREATE TABLE orders (
  id          SERIAL PRIMARY KEY,
  customer_id INTEGER NOT NULL,
  product_id  INTEGER NOT NULL,
  amount      NUMERIC(10,2) NOT NULL,
  created_at  TIMESTAMPTZ NOT NULL
);

CREATE TABLE customers (
  id      SERIAL PRIMARY KEY,
  name    TEXT NOT NULL,
  country TEXT NOT NULL
);
```

The query must return, for each country:
1. `country` — the country name
2. `total_revenue` — sum of all order amounts
3. `order_count` — total number of orders
4. `avg_order_value` — average order amount, rounded to 2 decimal places
5. `top_customer` — the name of the customer with the highest total spend in that country
   (break ties by customer name ascending)
6. `revenue_pct` — this country's share of global revenue, as a percentage rounded to 1 decimal place

Requirements:
- Use at least one CTE
- Use a window function for `revenue_pct`
- Order results by `total_revenue` descending
- Add a comment above each CTE explaining what it computes