Authentication Improvements

Improvements

• Add shared dev GitHub OAuth App for contributors
• Add .mcp.json trust gating for workspace MCP server configs (#797)
• Add AWS Bedrock auth error detection and notifications
• Add documentation website with Fumadocs
• Add Vercel deployment for docs site

Fixes

• Add warning toasts for branch sync rejection and hide banner by default
• Update outbound links from chatml.dev to chatml.com
• Extend deep link support to Linux and drop AppImage target

Misc

• Fix Windows OAuth deep link redirect on cold start
• Clarify why GitHub OAuth dev credentials are committed