Use JSON for known checksums (#415)

Ports the hardening from astral-sh/setup-uv#1025 to ruff-action.\n\nThis
stores generated checksums as JSON data behind a small typed TypeScript
wrapper, preventing values sourced from release metadata from being
mixed into generated executable code. It also updates the checksum
workflow and packaged action artifacts, and adds a regression test for
code-like keys and escaped checksum values.\n\nTests: npm run build, npm
run check, npm test, npm run package

tsconfig.json

@@ -5,6 +5,7 @@
     "module": "esnext",
     "moduleResolution": "bundler",
     "noImplicitAny": true,
+    "resolveJsonModule": true,
     "strict": true,
     "target": "ES2022"
   },