fix: resolve ESLint unused variable errors

Fixed 6 ESLint no-unused-vars errors across 4 files by prefixing
unused parameters with underscores per project conventions:

- scripts/popup-main.js: Updated updatePageInfo, copyToClipboard,
  and calculateReadabilityScore to use underscore-prefixed params
- src/services/ai-service.js: Updated makeProviderRequest param
- tests/e2e/extension-loading.spec.js: Renamed context to _context
- tests/integration/extension-workflow.test.js: Removed unused
  result assignment

All unit tests pass and linting now reports 0 errors (8 acceptable
warnings for console statements in logging utilities).

Author: aaron-seq

scripts/popup-main.js

@@ -435,7 +435,7 @@ class PopupInterfaceManager {
     return text.replace(/\n/g, '<br>').replace(/\*\*(.*?)\*\*/g, '<strong>$1</strong>');
   }
 
-  updatePageInfo(title, status) {
+  updatePageInfo(title, _status) {
     const titleEl = document.getElementById('current-page-title');
     if (titleEl) titleEl.textContent = title;
   }
@@ -481,7 +481,7 @@ class PopupInterfaceManager {
     const text = el.innerText;
     navigator.clipboard.writeText(text).then(() => {
       this.showSuccessToast('Copied to clipboard');
-    }).catch(err => {
+    }).catch(_err => {
       this.showErrorToast('Failed to copy');
     });
   }
@@ -504,7 +504,7 @@ class PopupInterfaceManager {
   }
   refreshAnalysisCards() {}
   updateLanguageDetection() {}
-  calculateReadabilityScore(text) { return { score: 80, level: 'Easy' }; }
+  calculateReadabilityScore(_text) { return { score: 80, level: 'Easy' }; }
 
   displayAnalysisResult(type, data) {
     const el = document.getElementById(`${type}-result`);

src/services/ai-service.js

@@ -254,7 +254,7 @@ export class AIService {
    * @param {Object} requestParams - Request parameters
    * @returns {Promise<Object>} Provider response
    */
-  async makeProviderRequest(requestParams) {
+  async makeProviderRequest(_requestParams) {
     // This would interface with the actual AI provider APIs
     // For now, return a mock response
     return {

tests/e2e/extension-loading.spec.js

@@ -32,7 +32,7 @@ test.describe('Extension Loading', () => {
     expect(extensionErrors).toHaveLength(0);
   });
 
-  test('should create context menu items', async ({ page, context }) => {
+  test('should create context menu items', async ({ page, context: _context }) => {
     await page.goto('https://example.com');
 
     // Select some text to trigger context menu

tests/integration/extension-workflow.test.js

@@ -38,7 +38,7 @@ describe('Extension Integration Workflow', () => {
       const messageHandler = chrome.runtime.onMessage.addListener.mock.calls[0][0];
 
       // Execute handler - Note: the handler is async but returns true immediately
-      const result = messageHandler(message, sender, sendResponse);
+      messageHandler(message, sender, sendResponse);
 
       // Verify response is eventually sent
       await vi.waitFor(() => {