Added new auth-related methods and events to mcp server

[etraut-openai]

This PR adds the following:

• A getAuthStatus method on the mcp server. This returns the auth method currently in use (chatgpt or apikey) or none if the user is not authenticated. It also returns the "preferred auth method" which reflects the preferred_auth_method value in the config.
• A logout method on the mcp server. If called, it logs out the user and deletes the auth.json file — the same behavior in the cli's /logout command.
• An authStatusChange event notification that is sent when the auth status changes due to successful login or logout operations.
• Logic to pass command-line config overrides to the mcp server at startup time. This allows use cases like codex mcp -c preferred_auth_method=apikey.

[chatgpt-codex-connector]

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[etraut-openai]

@bolinfest, ready for another round of review. I incorporated feedback from your last round:

1. Added ServerNotification enum and updated send_notification to accept it.
2. Reversed the dependency between the protocol and logon crates by moving AuthMode from the latter to the former.
3. Precompute Config with overrides and pass it to mcp server rather than threading config overrides down the call chain.

[etraut-openai]

@bolinfest, I incorporated your latest round of feedback. The serialization code is now much simpler and cleaner! The key was to use the serde content = "data" directive. This isolates the payload from the "type" discriminator field, which makes serialization much simpler.

I think it's ready for another (hopefully final) round of review.

[bolinfest]

Nice work, but please address comments before submitting!