v0.3.0 – Validation State API & Diagnostics Improvements

✨ New Features

• Added controller.getValidationState() API
• Introduced structured validation state:
  • is_valid
  • error_count
  • warning_count

🔁 Changes

• Removed onValidationChange callback
• Replaced callback-based validation reporting with pull-based state API
• Improved JSON diagnostics handling

🛠 Internal

• Refactored JSON validation pipeline
• Added validation state field + dispatch flow
• Improved diagnostics stability