Add Waterfall Chart & Request Inspector

Features Added:
- Interactive waterfall timeline visualization
- Color-coded timing bars (DNS, Connect, SSL, TTFB, Download)
- Request filtering by resource type (HTML, JS, CSS, Images, Fonts)
- Detailed request inspector dialog with timing breakdown
- HAR data extraction from Lighthouse results
- Size/compression metrics display
- Third-party resource identification
- Render-blocking resource detection

Technical Implementation:
- Created lib/har-parser.js for network data extraction
- Built waterfall.html with SVG-based timeline renderer
- Added waterfall.js with interactive controls
- Integrated HAR generation into test runner workflow
- Updated main UI with View Waterfall link

lib/runner.js

@@ -141,9 +141,15 @@ async function _executeTest(url, options) {
       isMobile: isMobile
     };
 
-  // Save JSON Summary
+    // Save JSON Summary
     const jsonPath = path.join(reportDir, `${testId}.json`);
     fs.writeFileSync(jsonPath, JSON.stringify(summary, null, 2));
+    
+    // Parse and save HAR data for waterfall
+    const harParser = require('./har-parser');
+    const harData = harParser.parseHAR(lhr);
+    const harPath = path.join(reportDir, `${testId}.har.json`);
+    fs.writeFileSync(harPath, JSON.stringify(harData, null, 2));
 
     await chrome.kill();