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.

pre-commit/rules.yml

@@ -1,4 +1,3 @@
----
 # Validation rules for pre-commit action
 # Generated by update-validators.py v1.0.0 - DO NOT EDIT MANUALLY
 # Schema version: 1.0
@@ -8,7 +7,6 @@
 # Rules are automatically applied by validate-inputs action when this
 # action is used.
 #
-
 schema_version: '1.0'
 action: pre-commit
 description: Runs pre-commit on the repository and pushes the fixes back to the repository