chore: upgrade borp to 1.0 and drop Node 18/20 in CI

[mcollina]

Summary

• upgrade borp from ^0.21.0 to ^1.0.0
• update tests and fixtures for borp 1.0 TypeScript runtime rules (.ts imports and import type)
• update migration loader to recognize TypeScript files (.ts, .mts, .cts) in addition to JavaScript files
• update CI Node matrix from 18.x/20.x to 22.x/24.x
• fix GitHub Actions versions to valid releases (actions/checkout@v4 and actions/setup-node@v4)
• bump additional dependencies: prettier to ^3.8.1 and semver to ^7.7.4
• remove @types/rfdc (rfdc ships its own declarations)
• ignore local agent artifacts in .gitignore (.pi/ and AGENTS.md)

TypeScript / publish configuration updates

• split development vs publish TypeScript configs
• tsconfig.json is now development/typecheck oriented:
  • noEmit: true
  • allowImportingTsExtensions: true
  • verbatimModuleSyntax: true
• tsconfig.build.json is now publishing oriented:
  • noEmit: false
  • declaration/declarationMap/sourceMap enabled
  • rootDir: src, outDir: dist
  • rewriteRelativeImportExtensions: true
• add npm script: typecheck
• keep package surface unchanged (no exports field added)

Validation

• npm run typecheck
• npm run lint
• npm test
• npm run build
• npm pack --dry-run

Pack dry-run includes dist/lib/semgrator.js and dist/lib/semgrator.d.ts as expected.

Dependency check

Remaining outdated entry:

• @types/node (latest is 25.x; project currently pins ^24.x)

[mcollina]

Follow-up done: removed because ships its own (v1.4.1). Build, lint, and tests all still pass.

[mcollina]

Follow-up done: removed the @types/rfdc devDependency because rfdc ships its own TypeScript declarations. Build, lint, and tests still pass.