Issue Description

Add comprehensive JSON Schema validation capabilities to the existing frontmatter validation system in HVE Core. This enhancement will provide developers with schema-based validation for different types of markdown files, ensuring consistent frontmatter structure and reducing validation errors.

Current State

• Basic frontmatter validation exists in Validate-MarkdownFrontmatter.ps1
• No schema-based validation for different content types
• Limited type checking and pattern validation

Proposed Solution

Implement a comprehensive JSON Schema validation system that includes:

• Schema definitions for different markdown content types (docs, instructions, prompts, chatmodes, root community files)
• Dynamic schema selection based on file patterns
• Enhanced PowerShell script with native JSON Schema validation capabilities
• VS Code IntelliSense support for frontmatter editing

Benefits

• Consistent frontmatter structure across different content types
• Better developer experience with IntelliSense support
• Automated validation in CI/CD pipeline
• Extensible schema system for future content types

Implementation Details

• Use PowerShell native JSON processing (no external dependencies)
• Create modular schema files with inheritance support
• Add EnableSchemaValidation parameter to existing validation script
• Configure VS Code workspace for schema-aware editing

Additional Context

This feature will enhance the existing linting infrastructure by providing type-specific validation rules for frontmatter, making it easier to maintain consistent documentation standards across the HVE Core project.