[codex] Prepare ZeroEngine for OSS applications

[liuzqk]

Summary

Prepare ZeroEngine as a public OSS Unity package repository for reuse and application review.

• add root README, MIT license, contribution, support, security, changelog, and GitHub templates
• document OSS graduation criteria and OpenAI OSS application notes
• normalize UPM package metadata with MIT license and repository directory fields
• add a README for the DataToolkit package

Validation

• Parsed all package.json files with PowerShell ConvertFrom-Json
• Verified every com.zerogamestudio package has a README
• Verified package metadata declares MIT license and https://github.com/liuzqk/zeroengine.git repository URL
• Searched for stale invalid repository/license wording
• Ran git diff --check

[github-actions]

Unity Test Report

360 tests  ±0   360 ✅ ±0   0s ⏱️ ±0s
 34 suites ±0     0 💤 ±0 
  1 files   ±0     0 ❌ ±0 

Results for commit 90f1323. ± Comparison against base commit d239cb8.

[liuzqk]

Superseded by #3 with the same repository cleanup under a normal maintenance branch.