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>

plugins/contract-validator/skills/mcp-tools-reference.md

@@ -16,6 +16,7 @@ Available MCP tools for contract-validator operations.
 | `validate_compatibility` | Check two plugins for conflicts |
 | `validate_agent_refs` | Check agent tool references exist |
 | `validate_data_flow` | Verify data flow through agent sequence |
+| `validate_workflow_integration` | Check domain plugin exposes required advisory interfaces |
 
 ### Report Tools
 | Tool | Description |
@@ -53,6 +54,13 @@ Available MCP tools for contract-validator operations.
 3. Build Mermaid diagram from results
 ```
 
+### Workflow Integration Check
+```
+1. validate_workflow_integration(plugin_path, domain_label)  # Check single domain plugin
+2. For each domain in domain-consultation.md detection rules:
+     validate_workflow_integration(domain_plugin_path, domain_label)
+```
+
 ## Error Handling
 
 If MCP tools fail: