refactor: inline node-setup across Node.js actions

Phase 6A: Remove node-setup abstraction layer and inline Node.js setup.

Changes:
- Replace node-setup calls with direct actions/setup-node@v6.0.0
- Inline package manager detection (lockfile-based)
- Add Corepack enablement and package manager installation
- Use Node.js 22 as default version

Actions migrated (5):
- prettier-lint: Inline Node.js setup + package manager detection
- biome-lint: Inline Node.js setup + package manager detection
- eslint-lint: Inline Node.js setup + package manager detection
- pr-lint: Inline Node.js setup (conditional on package.json)
- npm-publish: Inline Node.js setup + package manager detection

Removed:
- node-setup/action.yml (371 lines)
- node-setup/README.md, rules.yml, CustomValidator.py
- _tests/unit/node-setup/validation.spec.sh
- _tests/integration/workflows/node-setup-test.yml
- validate-inputs/tests/test_node-setup_custom.py

Documentation updates:
- CLAUDE.md: Remove node-setup from action list (26 actions)
- generate_listing.cjs: Remove node-setup mappings
- update-validators.py: Remove node-setup custom validator

Result: 26 actions (down from 27), eliminated internal dependency layer.

CLAUDE.md

@@ -71,7 +71,7 @@
 
 Flat structure. Each action self-contained with `action.yml`.
 
-**30 Actions**: Setup (node-setup, language-version-detect), Utilities (action-versioning, version-file-parser),
+**26 Actions**: Setup (language-version-detect), Utilities (action-versioning, version-file-parser),
 Linting (ansible-lint-fix, biome-lint, csharp-lint-check, eslint-lint, go-lint, pr-lint, pre-commit, prettier-lint, python-lint-fix, terraform-lint-fix),
 Testing (php-tests, php-laravel-phpunit, php-composer), Build (csharp-build, go-build, docker-build),
 Publishing (npm-publish, docker-publish, csharp-publish),