Support engine selection for Playwright Check Suites [RED-428]

[sorccu]

Summary

Adds support for selecting the JavaScript engine (Node.js or Bun) and version for Playwright Check Suites, with manual configuration, automatic detection, and rule-based version resolution.

Manual selection

import { PlaywrightCheck, Engine } from 'checkly/constructs'

new PlaywrightCheck('login-test', {
  name: 'Login E2E',
  playwrightConfigPath: './playwright.config.ts',
  engine: Engine.node('24'),  // or Engine.bun('1.3')
})

Automatic detection

When engine is not set, auto-detects from project version files (in priority order):

1. .node-version
2. .nvmrc (skips lts aliases)
3. .tool-versions (nodejs / bun entries)
4. .bun-version
5. package.json engines.node / engines.bun (semver range via minVersion)

Version resolution

Both auto-detected and explicit versions are resolved through inlined engines.json rules:

• EOL versions are remapped with a SubstitutedPropertyValueDiagnostic warning (e.g., Node 18 → 22)
• Denied versions produce an InvalidPropertyValueDiagnostic error (e.g., Bun 2.x)
• Valid versions pass through without diagnostics
• The rules loader has an async signature to support future API-based rule loading

Changes

• Engine class — Engine.node() / Engine.bun() static factories with autocomplete hints for known versions
• Version resolution — engine-resolver.ts with semver range matching, follow chains, deny actions
• Rules loader — engine-rules-loader.ts with inlined rules (canonical source: monorepo/engines.json)
• Auto-detection — engine-detector.ts with rule resolution, cached per session
• Diagnostics — SubstitutedPropertyValueDiagnostic for remapped versions, InvalidPropertyValueDiagnostic for denied
• synthesize — only includes engine/engineVersion fields when set (omitted → backend defaults to null)

Depends on

• Monorepo: checkly/monorepo#1817 (merged)

Test plan

• 15 unit tests for engine resolver (rule matching, follow chains, deny, all versions)
• 3 sandbox integration tests (EOL warning, denied error, valid pass)
• All 972 existing tests pass