Add lifecycle metadata schema to source JSON

[GarthDB]

Part of Epic #596

Problem

Current tokens lack lifecycle information (introduced, deprecated, removed dates) making it hard to:

• Generate meaningful diff reports
• Provide migration guidance
• Track token evolution over time

Solution

Add optional lifecycle metadata to source JSON format:

{
  "focus-indicator-color": {
    "value": "{blue-800}",
    "uuid": "fe914904-a368-414b-a4ac-21c0b0340d05",
    "lifecycle": {
      "introduced": "13.0.0",
      "status": "stable"
    }
  }
}

Implementation

• Design lifecycle metadata schema
• Add to existing source JSON (non-breaking)
• Update build system to process lifecycle data
• Generate enhanced output formats with lifecycle info

Acceptance Criteria

• Schema designed and documented
• Added to source JSON without breaking existing consumers
• Build system processes lifecycle metadata
• Enhanced diff generator uses lifecycle data

Keywords: lifecycle, metadata, schema, non-breaking