Upgrade monaco-editor to 0.55.1 and fix breaking API changes

[Copilot]

Monaco-editor 0.55.0 introduced breaking changes by moving nested namespaces (languages.typescript, languages.json, etc.) to top-level exports. The existing code used the deprecated API, causing TypeScript compilation failures.

Changes

• Updated monaco-editor: 0.53.0 → 0.55.1 (latest stable)
• Fixed TypeScript namespace usage: Migrated from monaco.languages.typescript.typescriptDefaults to top-level typescript.typescriptDefaults export
• Added Window type extension: Declared MonacoEnvironment property on Window interface to resolve TypeScript compilation error
• Updated test mocks: Reflected new API structure in Jest mocks

Example

// Before (deprecated in 0.55.0)
import * as monaco from 'monaco-editor';
monaco.languages.typescript.typescriptDefaults.setEagerModelSync(true);

// After
import * as monaco from 'monaco-editor';
import { typescript } from 'monaco-editor';
typescript.typescriptDefaults.setEagerModelSync(true);

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