feat(contract-validator): add validate_workflow_integration tool (v5.7.1)

Domain Advisory Pattern Hardening - patch release to close gaps from v5.6.0/v5.7.0:

## Added
- New `validate_workflow_integration` MCP tool validates domain plugins expose
  required advisory interfaces (gate command, review command, advisory agent)
- New `MISSING_INTEGRATION` issue type for workflow integration validation
- New `WorkflowIntegrationResult` Pydantic model for structured validation output
- `integrates_with` field on viz-platform and data-platform in marketplace.json
  declaring projman integration metadata
- 4 new test cases for workflow integration validation

## Fixed
- scripts/setup.sh banner version updated from v5.1.0 to v5.7.1

## Documentation
- Updated mcp-tools-reference.md with new tool
- Updated validation-rules.md with Workflow Integration Checks section
- Added /design-gate, /design-review, /data-gate, /data-review to COMMANDS-CHEATSHEET
- Added contract-validator to CONFIGURATION.md plugin table
- Updated README.md Contract Validator tools table

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -4,6 +4,18 @@ All notable changes to the Leo Claude Marketplace will be documented in this fil
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
+## [5.7.1] - 2026-02-02
+
+### Added
+- **contract-validator**: New `validate_workflow_integration` MCP tool — validates domain plugins expose required advisory interfaces (gate command, review command, advisory agent)
+- **contract-validator**: New `MISSING_INTEGRATION` issue type for workflow integration validation
+- **marketplace.json**: `integrates_with` field on viz-platform and data-platform declaring projman integration metadata
+
+### Fixed
+- `scripts/setup.sh` banner version updated from v5.1.0 to v5.7.1
+
+---
+
 ## [5.7.0] - 2026-02-02
 
 ### Added