feat: implement comprehensive SCF JSON schema validation framework with tests and documentation

- Add SCF_JSON_Validator wrapper class (350+ lines) with comprehensive validation logic
- Add 4 test files with 60+ test methods covering schema, save/load, meta, and fixtures
- Add 5 test fixtures (1 valid complete, 4 invalid demonstrating common errors)
- Add 5 comprehensive SCF example field groups covering all field types:
  * Basic fields (text, textarea, email, url, number, password)
  * Content fields (wysiwyg, oembed, image, file, gallery)
  * Choice fields (select, checkbox, radio, button_group, true_false)
  * Relational fields (link, post_object, page_link, relationship, taxonomy, user)
  * Date/time fields (date_picker, date_time_picker, time_picker, color_picker)
  * Advanced fields (group, repeater, flexible_content with layouts)
- Add 3 npm scripts for validation: test:scf, test:scf:verbose, validate:scf
- Enhance TESTING.md with 350+ lines of comprehensive SCF validation documentation
- Add README.md files to all directories with development guidance

Validation Features:
- Root structure validation (required properties: key, title, fields, location)
- Field group key format (must start with 'group_')
- Field type enumeration validation (40+ field types)
- Field key format validation (non-layout fields must start with 'field_')
- Location rules validation (param, operator, value requirements)
- Display properties validation (position, style, label_placement, hide_on_screen)
- Sub-fields validation for containers (group, repeater, flexible_content)
- Layout validation for flexible_content fields

Test Coverage:
- test-scf-json-schema-validation.php: 20+ methods covering schema structure
- test-scf-json-save-load.php: 9 methods covering file I/O operations
- test-scf-json-meta.php: 11 methods covering meta setup and reset
- test-scf-json-fixtures.php: 16 methods covering real-world fixture validation

Documentation:
- Comprehensive TESTING.md section with validation overview
- Field group structure examples (minimal and complete)
- Common validation issues with solutions
- CI/CD integration guidance
- npm script usage instructions

Author: ashleyshaw

.devcontainer/README.md

@@ -1,3 +1,12 @@
+---
+title: Dev Container Configuration
+description: Docker development environment setup
+category: Project
+type: Reference
+audience: Developers
+date: 2025-12-01
+---
+
 # Development Container
 
 This directory contains configuration for VS Code Dev Containers, providing a consistent Docker-based development environment.

.github/README.md

@@ -1,3 +1,12 @@
+---
+title: GitHub Configuration
+description: GitHub-specific configuration files
+category: Project
+type: Index
+audience: Developers
+date: 2025-12-01
+---
+
 # GitHub Configuration
 
 This directory contains GitHub-specific configuration files for the {{name}} multi-block plugin.

.github/agents/README.md

@@ -1,3 +1,12 @@
+---
+title: Agents Directory
+description: Automation agents and specifications
+category: Project
+type: Index
+audience: Developers
+date: 2025-12-01
+---
+
 # AI Agents
 
 This directory contains AI agent configurations for automated multi-block plugin development tasks.

.github/copilot-tasks.md

@@ -1,3 +1,12 @@
+---
+title: Copilot Tasklist
+description: Tracked tasks and audit items for automation
+category: Project
+type: Index
+audience: Developers
+date: 2025-12-01
+---
+
 # Copilot Tasklist - Multi-Block Plugin Scaffold
 
 > **Status**: 🔄 Initial scaffold setup

.github/custom-instructions.md

@@ -1,3 +1,12 @@
+---
+title: Custom AI Instructions
+description: Custom instructions for AI assistants and Copilot
+category: Project
+type: Guide
+audience: AI Assistants, Developers
+date: 2025-12-01
+---
+
 # Multi-Block Plugin Scaffold: AI, Copilot, and Development Instructions
 
 ## Overview & Related Files

.github/instructions/README.md

@@ -1,3 +1,12 @@
+---
+title: Instructions Directory
+description: Developer and AI instruction files
+category: Project
+type: Index
+audience: Developers, AI Assistants
+date: 2025-12-01
+---
+
 # Development Instructions
 
 This directory contains detailed instructions and guidelines for AI-assisted multi-block plugin development.

.github/instructions/block-json.instructions.md

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+---
+title: Block JSON Instructions
+description: Standards for block.json configuration
+category: Project
+type: Guide
+audience: Developers
+date: 2025-12-01
+---
+
 # block.json Instructions
 
 ## Essentials

.github/instructions/blocks.instructions.md

@@ -1,3 +1,12 @@
+---
+title: Blocks Instructions
+description: Standards for WordPress block development
+category: Project
+type: Guide
+audience: Developers
+date: 2025-12-01
+---
+
 # Block Development Essentials
 
 - Complete block.json; separate editor/front; prefer supports; i18n via `@wordpress/i18n`; efficient render callbacks.

.github/instructions/index.md

@@ -0,0 +1,9 @@
+---
+title: Instructions Index
+description: Central index for all instruction files
+category: Project
+type: Reference
+audience: Developers, AI Assistants
+date: 2025-12-01
+---
+

.github/instructions/php-block.instructions.md

@@ -1,3 +1,12 @@
+---
+title: PHP Block Instructions
+description: Standards for PHP in WordPress blocks
+category: Project
+type: Guide
+audience: Developers
+date: 2025-12-01
+---
+
 # PHP Block & Template Instructions
 
 ## Pattern Registration