Publish to JSR

[EthanThatOneKid]

Summary

Publish the difflint package to JSR (JavaScript Registry) so it can be consumed as a first-class Deno/TypeScript module.

Tasks

• Register the package scope and name on jsr.io (e.g. @fartlabs/difflint)
• Update deno.json with the correct JSR package name and version
• Ensure all public API exports are properly documented with JSDoc
• Verify the module passes deno publish --dry-run without errors
• Set up a GitHub Actions workflow for automated publishing on release/tag
• Publish the initial version to JSR

Context

The package is already structured as a Deno module with a mod.ts entry point and deno.json exports. The current deno.json has "name": "@ethan/difflint" which should be updated to the correct scope.