refactor: comprehensive codebase reorganization with path aliases (v0…

[stevez]

….11.1)

Restructured entire codebase into focused domain folders and implemented TypeScript path aliases for better maintainability and scalability.

Phase 2-6 Modular Reorganization:

• Organized utilities into utils/ folder (config, logger, constants, dev-mode-extractor)
• Organized CLI into cli/ folder structure (commands/merge.ts, commands/init.ts)
• Organized core processing modules into core/ folder (processor, v8-reader, reporter, sourcemap-loader)
• Organized worker modules into worker/ folder (ast-worker, pool)
• Organized merger module into merger/ folder (core, printer, utils)
• Created centralized index.ts exports for all modules

Path Aliases Implementation:

• Configured TypeScript path aliases with @/ prefix in tsconfig.json
• Added tsc-alias to build script for path resolution in compiled JavaScript
• Updated vitest.config.ts with resolve.alias configuration
• Migrated 35+ files across all modules to use path aliases
• Updated dynamic imports and vi.mock paths in CLI commands and tests

TypeScript Improvements:

• Fixed type inference issues in test files with FileCoverageData casts
• Fixed incorrect test assertions with extra parameters
• Removed non-existent exports (setVerbose, WorkerResult)

Final Structure - 9 domain-focused folders:

• cli/ - Command-line interface and commands
• core/ - Core processing modules (processor, reporter, reader, source maps)
• utils/ - Shared utilities (config, logger, constants, extractors)
• worker/ - Worker thread parallelization
• merger/ - Coverage merging logic
• converter/ - V8-to-Istanbul conversion
• parsers/ - Bundler-specific URL parsers
• collector/ - Coverage collection (CDP, dev mode, production)
• playwright/ - Playwright test fixtures

All 686 tests passing with full TypeScript type checking. No API changes - purely internal code organization improvement.