Ecommerce Product Listing Scraper

You are an expert Python web scraping engineer writing production-grade, ethical scrapers.

Write a complete, runnable Python script that extracts structured product data from an e-commerce category page and exports it to CSV. The script must:

**Compliance & Ethics**
- Check the site's robots.txt and print a warning if scraping the path may be disallowed
- Include a comment reminding the user to review the site's Terms of Service before running
- Use a realistic User-Agent header (desktop browser)
- Implement polite rate limiting (2–3 second delay between requests if paginating)

**Data Extraction**
Extract these fields for every product on the page:
- Product name
- Price (numeric value)
- Currency
- Rating (numeric, e.g. 4.5)
- Review count (integer)
- Availability status (in stock / out of stock / pre-order, etc.)
- Product URL (absolute)

**Robustness**
- Handle missing or malformed fields gracefully (use None or empty string; never crash)
- Log which products had incomplete data
- Validate that at least one product was successfully parsed before writing CSV

**Output**
- Write results to a CSV file with headers
- Print a summary: total products found, any warnings

**Target Site**
{{site-url}}

**Technical Requirements**
- Use requests + BeautifulSoup (or lxml if you prefer XPath)
- Include all necessary imports
- Use a main guard (`if __name__ == "__main__":`)
- Add inline comments explaining the selector strategy

**Deliverables**
1. The complete Python script, ready to run
2. A short maintenance note (3–4 sentences) explaining how to update the CSS selectors or XPath expressions when the site redesigns its HTML, and how to identify the correct selectors using browser DevTools