/mcp hangs when authorizing a plugin-provided connector (Stripe)

Attempting to authorize the Stripe plugin connector (`plugin:stripe:stripe`) via `/mcp` in an interactive session hangs / doesn't complete. Connector status remains `needs_auth` even after the user reports completing authorization elsewhere (checked via session status — `reconnect` correctly reports it needs a user-driven sign-in, but the `/mcp` flow itself did not complete for the user).

Reproduced in the Claude Code desktop app (Code tab).

Steps to reproduce:
1. Have a plugin-provided MCP server (e.g. the Stripe plugin) in `needs_auth` state.
2. Run `/mcp` in an interactive session to authorize it.
3. The authorization flow hangs / does not complete.

Start by reproducing the `/mcp` flow with the Stripe plugin connector in `needs_auth`, then compare its behavior with session status and `reconnect`, which correctly reports that sign-in is required. Done means authorization completes in the interactive flow and the connector no longer remains in `needs_auth` after the user finishes signing in.

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