Bug: Failed manual connection leaves un-modifiable ghost server entry

[brandonja991]

Summary

When manually adding an MCP server and the connection attempt fails, MCP Inspector still creates a server entry that cannot be edited or removed through normal means. The failure is also silent (no visible error/toast). Later, if a user tries to import a server with the same name from a client config file, the import fails with an "already exists" error, even though the original entry never successfully connected and isn't visibly manageable.

Environment

• Tool: MCP Inspector v2
• Affected transports: streamable-http, sse (manual configuration flow)

Steps to Reproduce

1. MCP Inspector > Add Server > Add manually.
2. Set a server name.
3. Select transport streamable-http or sse.
4. Enter a URL that will fail to connect (in my case, the server returned HTTP 500 because required headers/cookies could not be set — see companion header/cookie ticket).
5. Submit. Observe: the failure is silent — no error message or indication that the connection failed.
6. Now go to MCP Server > Add Server > Import from client config > From file...
7. Select a valid client config file that contains a server entry with the same name used in step 2.
8. Observe: an error stating the MCP server already exists.

Expected Behavior

• A failed manual connection attempt should surface a clear, visible error to the user (not fail silently).
• A server entry that failed to connect should either not persist, or should be visible/editable/removable in the UI so the name can be reused or the entry fixed.
• Importing a server from client config should not be blocked by a failed/ghost entry that the user cannot see or manage.

Actual Behavior

• The failed manual connection attempt produces no visible error (silent failure).
• A "ghost" entry is created under the hood for that server name that does not appear to be editable/removable through the normal UI.
• Attempting to import a client-config server with the same name later fails with a duplicate-name/"already exists" error, with no clear path to resolve it (e.g., rename, delete the ghost entry, or overwrite).

Suggested Fix

1. Surface connection failures to the user immediately (toast/inline error) instead of failing silently.
2. Do not persist a server entry if the connection attempt fails, OR make any persisted-but-failed entries visible and manageable (edit/delete) in the server list.
3. When importing from client config and a name collision occurs, provide the user an option to overwrite/replace the existing (especially failed/unconnected) entry rather than only blocking with an error.