chore(internal): Add scripts for debug compilation and testing

[jsklan]

Description

compile:debug -- compiles projects with the --sourceMap flag for type linking
test:debug -- runs pnpm test with --inspect flag

Changes Made

• also added configs to turbo.json to hook into these commands
• still requires manual attachment of debugger after test process starts
  • Cmd+Shift+P -> Debug: Attach to Node Process
• also modified top level depcheck script to use turbo
• Updated CONTRIBUTING.md with the following section:

Debugging

For debugging TypeScript code in tests, use the debug compilation and test scripts:

1. Compile for debugging: pnpm compile:debug

   • Required for all debug workflows
   • Uses --sourceMap flag to generate source maps for proper TypeScript debugging
   • Slower than standard compilation, which is why source maps are disabled by default

2. Run tests with debugger: pnpm test:debug [test-file-name]

   • Starts tests with Node.js debugger enabled
   • Optionally specify a test file name to run only that test
   • Manually attach VS Code debugger by opening Command Palette (Cmd+Shift+P) and selecting "Debug: Attach to Node > Process"

Limitations: Debug scripts only work with vitest tests. Some -- but not all -- of the workflows they won't work with:

• Local Fern CLI builds (compiled to single executable CJS file)
• Generators (run in Docker containers, not all written in TypeScript)

[promptless]

✅ No documentation updates required.