refactor: Use tsconfig-paths library for robust config parsing

[lightninglu10]

Summary

Replaces the fragile regex-based tsconfig.json parsing with the well-tested tsconfig-paths library.

Problem

The previous implementation used regex to parse tsconfig.json:

const pathsMatch = tsconfigContent.match(/"paths"\s*:\s*\{([^}]+)\}/);

This approach had several limitations:

• Could fail on multi-line path definitions with nested braces
• Didn't follow the extends field to resolve inherited configurations
• Couldn't handle all JSON5 syntax TypeScript allows (comments, trailing commas)

Solution

Use the tsconfig-paths library which:

• Uses json5 parser to handle comments and trailing commas
• Properly resolves extends chains
• Is well-tested and maintained
• Handles complex path patterns correctly

Changes

• Added tsconfig-paths as a dependency
• Replaced regex parsing with loadConfig() from tsconfig-paths
• Moved fs and path to top-level imports (also addresses refactor: Move fs/path to top-level imports in webpack plugin #39)
• Simplified the code significantly

Test plan

• npm run build passes
• npm test passes (104 tests)
• Tested with tsconfig files containing comments and extends

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