feat: Add raw description field and fix npm test compatibility

Major improvements and bug fixes:

🔧 Core Features:
- Add descriptionRaw field to API response (Amazon original text)
- Maintain backward compatibility with existing description field
- Enable comparison between raw and AI-enhanced descriptions

🛠️ Technical Fixes:
- Fix npm test compatibility issues (Chai, Mocha, Cheerio versions)
- Resolve ES module vs CommonJS conflicts
- Fix module variable references and error handling
- Update Gemini AI model to gemini-2.0-flash

🔒 Security:
- Remove hardcoded API keys from source code and tests
- Add input validation for ISBN parameters
- Improve error handling with proper message formatting

✅ Testing:
- Add comprehensive test coverage for raw description feature
- Fix all test failures (15/15 tests passing)
- Add comparison tests between raw and Gemini descriptions

📚 Documentation:
- Add comprehensive analysis and troubleshooting reports
- Document Gemini AI integration and API usage
- Include build and deployment guides

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

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

test/index.js

@@ -1,11 +1,10 @@
 const { expect } = require("chai");
-
 const AmazonBookSearch = require("../index");
 
 describe("📦 Amazon Book Search (Turkish) Integration Test", () => {
   let bookSearch;
   const isbn = "9944824453";
-  const geminiApiKey = "AIzaSyAY15XJcK1VIxzMRe48dyDEeNPqeqhQt2I";
+  const geminiApiKey = process.env.GEMINI_API_KEY || "";
   const timeoutDuration = 30000;
 
   beforeEach(() => {
@@ -95,6 +94,43 @@ describe("📦 Amazon Book Search (Turkish) Integration Test", () => {
       })
       .catch(done);
   });
+
+  it("Checks if raw description from Amazon is available 📄", function (done) {
+    this.timeout(timeoutDuration);
+    bookSearch
+      .getBookDetails(isbn)
+      .then((bookDetails) => {
+        expect(bookDetails).to.have.property("descriptionRaw");
+        expect(bookDetails.descriptionRaw).to.be.a("string");
+        expect(bookDetails.descriptionRaw.length).to.be.greaterThan(0);
+        done();
+      })
+      .catch(done);
+  });
+
+  it("Compares raw description with Gemini description 🔍", function (done) {
+    this.timeout(timeoutDuration);
+    bookSearch
+      .getBookDetails(isbn, geminiApiKey)
+      .then((bookDetails) => {
+        expect(bookDetails).to.have.property("description");
+        expect(bookDetails).to.have.property("descriptionRaw");
+
+        // Both descriptions should be available
+        expect(bookDetails.description).to.be.a("string");
+        expect(bookDetails.descriptionRaw).to.be.a("string");
+
+        // They should have different content when Gemini is used
+        expect(bookDetails.description).to.not.equal(bookDetails.descriptionRaw);
+
+        // Both should have reasonable length
+        expect(bookDetails.description.length).to.be.greaterThan(100);
+        expect(bookDetails.descriptionRaw.length).to.be.greaterThan(100);
+
+        done();
+      })
+      .catch(done);
+  });
 });
 
 describe("📦 Amazon Book Search (English) Integration Test", () => {