Add OAuth token injection for MCP servers using original identifiers

[sestinj]

Summary by cubic

Automatically injects OAuth tokens into MCP server connections using the original --mcp identifiers, reducing extra auth prompts and improving headless startup.

• New Features
  • Track original --mcp values (URLs or hub slugs) and map them to resolved MCP servers in ConfigService.
  • Fetch OAuth tokens via ide/mcp-auth using org or personal scope and inject as apiKey for remote SSE/HTTP servers before connecting.
  • Wire MCPService to AuthService and pass mcpOriginalIds into initialization; silent fallback if no token is available.

^{Written for commit ae4ab80f423389c3df98b61f6bc43abc68a85ace. Summary will update automatically on new commits.}