test: consolidate test mocks into reusable factories

- Create comprehensive mock factories in test-helpers.ts
  - Storage variants (with auth, minimal)
  - Workspace variants (running, stopped, failed, with build)
  - VSCode components (RemoteSSH, TreeView, StatusBar, QuickPick, Terminal, OutputChannel)
  - Provider factories (WorkspaceProvider, TreeDataProvider)
  - Other utilities (Remote, Commands, EventEmitter, Axios, ProxyAgent, Uri)

- Migrate all test files to use mock factories
  - api.test.ts: Replace inline process/WebSocket mocks, use createMockApi
  - commands.test.ts: Replace all inline mocks with factories
  - extension.test.ts: Consolidate context, provider, and remote mocks
  - workspaceMonitor.test.ts: Use getPrivateProperty helper, eliminate inline mocks
  - workspacesProvider.test.ts: Replace vscode module mock with factory
  - inbox.test.ts: Remove type casting patterns
  - headers.test.ts: Use createMockConfiguration
  - remote.test.ts: Update Storage mock to use factory

- Improve test quality and maintainability
  - Reduce 'as any' casts from 95 to 4 (96% reduction)
  - Eliminate all inline mock object definitions
  - Remove unsafe type casting patterns
  - Centralize mock creation logic
  - All 405 tests passing with 78.49% coverage

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

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

Author: jaggederest

CLAUDE.md

@@ -44,10 +44,11 @@ Current status: **74.35% overall unit test coverage** with 359 unit tests and 69
 
 ### Testing Priority Framework
 
-1. **Files with <50% coverage** need immediate attention (remote.ts: 49.21%, extension.ts: 38.68%)
+1. **Files with <50% coverage** need immediate attention (remote.ts: 49.51%)
 2. **Add incremental tests** - focus on measurable progress each session
 3. **Target coverage improvements** of 5-15 percentage points per file
 4. **ALWAYS use `yarn test:ci --coverage`** - never test individual files
+5. **Ignore coverage for test-helpers.ts** - this is a test utility file containing mock factories and helper functions
 
 ### Testing Patterns to Follow