feat: Add project-specific MCP server detection

[gvago]

Summary

Adds support for detecting and displaying project-specific MCP servers from .mcp.json files alongside global servers, providing users with a complete view of their MCP server configuration.

Changes Made

Core Functionality

• New readProjectMcpConfig(): Reads .mcp.json from current working directory
• Enhanced getAllMcpServers(): Now returns {active, disabled, project} instead of just {active, disabled}
• Project server detection: Automatically finds and displays project-specific servers

UI Improvements

• Visual distinction: Project servers show with 📁 folder icon and "(project - read-only)" label
• Read-only state: Project servers are disabled in the checkbox interface (cannot be toggled)
• Smart sorting: Project servers appear at bottom of list for better organization
• Updated messaging: Error messages now mention .mcp.json alongside other config files

Implementation Details

• Non-destructive: Project servers are never modified, only displayed
• Filtered from management: Project servers are excluded from toggle operations
• Type safety: Added optional disabled property to ServerToggleItem interface

Testing

Tested in a real project with .mcp.json containing:

{
  "mcpServers": {
    "supabase": {
      "command": "npx",
      "args": ["-y", "@supabase/mcp-server-supabase@latest", "--project-ref=..."]
    }
  }
}

Result: Successfully displays all servers with clear visual distinction:

• ✅ Global servers (toggleable)
• 📁 Project servers (read-only)

Benefits

1. Complete visibility: Users can see all MCP servers (global + project) in one view
2. No confusion: Clear labeling prevents accidental management attempts
3. Respects architecture: Project servers remain managed by Claude Code
4. Backward compatible: Existing functionality unchanged
5. Zero breaking changes: All existing workflows continue to work

Use Case

This addresses the common scenario where developers have:

• Global MCP servers (archon, playwright, shadcn-ui) managed via claude-ext
• Project-specific servers (supabase with credentials) managed via Claude Code's .mcp.json

Now users get a unified view while respecting the appropriate management boundaries.

Resolves #1