feat: publish compiled map JSON-IR artifacts from maps repo

[ronaldtse]

Summary

• add a canonical compiled JSON-IR artifact builder to the maps repo: .isc corpus → manifest.json, SHA256SUMS, maps/*.json
• add a workflow that validates the artifact on PRs, uploads it as an Actions artifact, and attaches tarballs/checksums to tagged GitHub Releases
• gives API deployments a data artifact to fetch into Worker Assets instead of bundling map JSON in @interscript/api-worker

Test plan

• npx -y tsx scripts/build-json-ir-artifact.mjs /Users/mulgogi/src/interscript/interscript-ts /tmp/interscript-maps-ir-test-ts
• local artifact contains 289 JSON maps + manifest + SHA256SUMS
• workflow YAML parses