[FEATURE] Add claude mcp auth <name> command for on-demand MCP authentication

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

There is currently no way to trigger MCP server authentication from the command line. The only way to authenticate an MCP server that requires OAuth is to start a session and initiate the flow via /mcp.

Proposed Solution

Add an auth (or login) subcommand to claude mcp:

``bash
# Trigger the OAuth flow for a specific MCP server
claude mcp auth <server-name>
``

Alternative Solutions

_No response_

Priority

Medium - Would be very helpful

Feature Category

CLI commands and flags

Use Case Example

``bash
# Add and authenticate an MCP server in one scripted flow
claude mcp add my-server --transport http --url https://example.com/mcp
claude mcp auth my-server
# Browser opens, user completes OAuth, token is stored
# Server is now ready to use in the next session
``

Additional Context

Other AI coding tools have already implemented this pattern:

• Codex: codex mcp login <name> — triggers OAuth authentication for a named MCP server
• Cursor: cursor mcp login <name> — same concept, authenticate an MCP server by name from the CLI