fix: prevent crash on malformed MCP server config (#5666) (#5673)

* fix: prevent crash on malformed MCP server config (#5666)

* fix: prevent crash on malformed MCP server config (#5666)

* fix: validate MCP connection before persisting server config

* fix: guard mcpServers type before iterating server list

* refactor: use typed empty-config error and extract MCP rollback helper

* fix: translate error messages and comments to English for consistency

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Co-authored-by: Soulter <905617992@qq.com>

Author: Clhikari