feat: add codemod for DEP0162 fs write coercion

[syhstanley]

Summary

Adds a codemod for DEP0162 — implicit coercion of objects in fs.write() and fs.writeFileSync().

• Wraps the data parameter with String() for fs.writeFile(), fs.writeFileSync(), fs.appendFile(), fs.appendFileSync(), fs.write(), and their fs/promises variants
• Skips already-safe types: string literals, template literals, Buffer.from(), new Uint8Array(), .toString(), String() wrappers
• Handles both CommonJS require('fs') and ESM import { writeFile } from 'node:fs/promises'
• Handles destructured imports

Test plan

• 8 test cases covering all examples from fs.write() and fs.writeFileSync() coercion to string #412
• No-change test for valid types (strings, Buffers, TypedArrays)
• Destructured import test
• ESM promises API test
• All 8 tests pass via npx codemod jssg test

Closes #412

🤖 Generated with Claude Code

[AugustinMauroy]

not too bad but:

for you info you have to use this structure of testing

Codemod leverages a before ("input") + after ("expected") snapshot comparison. Codemod supports 2 options:

• 👍 Single-file fixtures

  tests/
    some-test-case-description/
      input.ts
      expected.ts
    another-test-case-description/
      input.ts
      expected.ts
  

• 👎 Directory snapshot fixtures

  tests/
    input/
      some-test-case-description.ts
      another-test-case-description.ts
    expected
      some-test-case-description.ts
      another-test-case-description.ts
  

Use the Single-file fixtures option.

[syhstanley]

Thanks for your review! Please check the new commits.