[voischev]

Summary

• Replace tsup, AVA, XO and Clinton with tsc, native Node.js tests/assertions, c8 and ESLint.
• Remove Git hooks, commit-message tooling and generated changelog updates; reduce direct development dependencies from 20 to 7 and installed packages from 1352 to 175.
• Preserve all 49 existing tests in a shared synchronous suite and add coverage for closeAs on void tags. Run that suite against isolated production tarball installs on the runtime matrix.
• Make public declarations self-contained, including mixed nested content arrays, and add standalone CommonJS/ESM TypeScript consumers.
• Update README examples, contributor/release instructions, agent guidance and issue/PR templates.

This includes and updates the agent workflow guide from #76. Replacing the legacy repository linter also removes the external SchemaStore resolution failure that blocked that PR's CI.

Compatibility

• The published runtime requirement remains Node.js >=12; development and build tooling use Node.js 24.
• Runtime dependencies remain is-json ^2.0.1. The renderer does not load or depend on the parser at runtime, and standalone declaration consumers no longer need parser types installed.
• Keep parser 0.9 as a development-only round-trip fixture so the complete shared suite can run on Node.js 12. Validate current parser 0.13 separately through the core packed-package integration.
• Preserve the named CommonJS API, native ESM interop, enums and rendering behavior. Emit ES2019 CommonJS rather than a minified bundle.
• Keep TypeScript 4.3.5 consumer compatibility. No version bump is included; release notes are recorded under Unreleased.

Verification

• npm ci and npm run check passed on Node.js 24.22.1.
• 50 renderer tests passed; coverage is 100% statements/functions/lines and 96% branches, with enforced thresholds of 100%/100%/100%/95%.
• npm audit: 0 vulnerabilities (the original installation reported 66).
• Built with npm pack --ignore-scripts --pack-destination artifacts and tested the same tarball using npm run test:packed -- artifacts/posthtml-render-3.0.0.tgz --node <node-executable> on:
  • Node.js 12.0.0, 12.22.12, 14.21.3, 16.20.2, 18.20.8, 20.19.0, 22.12.0, 22.23.4, 24.22.1 and 26.12.1.
  • Each run executes the complete renderer suite, CommonJS/native ESM consumers, and a standalone TypeScript consumer with no parser installed. Node.js 12.0 uses the historical experimental ESM flag.
• Consumer declarations passed on TypeScript 4.3.5 and 6.0.3. Isolated CJS/ESM consumers combining the candidate renderer, parser 0.13.0 and core 0.16.7 also passed TypeScript 5.3.3 and 6.0.3, including mixed content and source-location ASTs.
• Core integration used its candidate tarball with parser 0.13 and this renderer override:

  npm run test:packed -- artifacts/posthtml-0.16.7.tgz --render ../posthtml-render/artifacts/posthtml-render-3.0.0.tgz

  58 core tests + 10 consumer tests passed on Node.js 20.19.0, 22.12.0, 22.23.4, 24.22.1 and 26.12.1; the existing skipped core test remains skipped.
• Workflow YAML parsed successfully; git diff --check passed.

CI now checks on Node.js 24, packs the checked build once, then tests that artifact on Node.js 12.0/12/14/16/18/20/22/24/26. npm and TypeScript run on development Node while the full JavaScript suite runs with the selected consumer executable.