chore: Fix all lint errors and remove unused code

- Fix 75 ESLint errors by updating eslint.config.mjs:
  - Add missing browser globals (MouseEvent, AbortController, Response, etc.)
  - Add Vite define global (__APP_VERSION__)
  - Configure @ts-nocheck to require descriptions
  - Add no-unused-vars rule for .mjs scripts

- Fix runtime bug in agent-output-modal.tsx (setOutput -> setStreamedContent)

- Remove ~120 unused variable warnings across 97 files:
  - Remove unused imports (React hooks, lucide icons, types)
  - Remove unused constants and variables
  - Remove unused function definitions
  - Prefix intentionally unused parameters with underscore

- Add descriptions to all @ts-nocheck comments (25 files)

- Clean up misc issues:
  - Remove invalid deprecation plugin comments
  - Fix eslint-disable comment placement
  - Add missing RefreshCw import in code-view.tsx

Reduces lint warnings from ~300 to 67 (all remaining are no-explicit-any)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/ui/tests/projects/new-project-creation.spec.ts

@@ -6,14 +6,12 @@
 
 import { test, expect } from '@playwright/test';
 import * as fs from 'fs';
-import * as path from 'path';
 import {
   createTempDirPath,
   cleanupTempDir,
   setupWelcomeView,
   authenticateForTests,
   handleLoginScreenIfPresent,
-  waitForNetworkIdle,
 } from '../utils';
 
 const TEST_TEMP_DIR = createTempDirPath('project-creation-test');

apps/ui/tests/projects/open-existing-project.spec.ts

@@ -17,7 +17,6 @@ import {
   setupWelcomeView,
   authenticateForTests,
   handleLoginScreenIfPresent,
-  waitForNetworkIdle,
 } from '../utils';
 
 // Create unique temp dir for this test run