Complete documentation for Agent Forge, co-authored with Claude.

Documentation includes:
- Overview: Product introduction, capabilities, and architecture
- Getting Started: Account setup, registration, login, and password management
- Chatting with Agents: Using the chat interface and file uploads
- Building Agents: Complete guide to creating and configuring agents including:
  * Model selection and system prompts
  * Generation settings (Temperature, Top P, Top K, Max Tokens)
  * Knowledge base integration
  * Security features (PII detection, prompt injection protection)
  * Access control and topic filters
- Knowledge Base: KB management and semantic search testing

Changes:
- Added 5 comprehensive documentation pages (27 sections total)
- Added 22 screenshots demonstrating all features
- Created Agent Forge as dedicated tab (positioned after Development tab)
- Added Agent Forge section to Home tab navigation
- Added Agent Forge card to welcome page
- Updated all internal navigation links
- Organized screenshots in pages/agent-forge/screenshots/

…nces

- Add mcp.mdx: new page documenting org-level and agent-level MCP configuration
  with screenshots, JSON config reference, field table, use cases, and best practices
- Add 3 MCP screenshots to Agent Builder section
- Update overview.mdx: remove "formerly Agent Studio", add MCP to capabilities
- Update getting-started.mdx: fix email subject "Agent Studio" → "Agent Forge"
- Update building-agents.mdx: add MCP callout near streaming section, add MCP to next steps
- Update docs.yml: add MCP Integration page to nav (home + agent-forge tabs), after Knowledge Base