docs: license OpenCode plugin for public distribution

[hopeatina]

Summary

• Bump the alpha package version to 0.1.0-alpha.2.
• Change package metadata from UNLICENSED to MIT.
• Add the standard OrgX MIT LICENSE file and include it in the npm package files list.

Verification

• npm run type-check
• npm test
• npm run build
• npm pack --dry-run --json confirmed 0.1.0-alpha.2 includes LICENSE
• git diff --check

Marketplace impact

This removes the public-distribution/license blocker noted in the OrgX marketplace submission packet for OpenCode directory/community review surfaces. Publishing the GitHub release for 0.1.0-alpha.2 remains the separate step that updates npm registry metadata.