Allow customizing the user home directory (.gemini) via an environment variable on Windows

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Description of the feature request:

I used the env-var "XDG_CONFIG_HOME" and "GEMINI_USER_HOME" to specify the saved path of check-points, but failed. Does cli has the features to redirect the saved path?

What problem are you trying to solve with this feature?

1. the default saved path likes "C:\Users\userName.gemini\tmp\c24962b5cfa73409417097fe1da9a93e662535152e2e26a4eb71f79dbfd777f1", whiich can not be customized
2. when the names of checkpoints are Chinese, the saved files can not be found, but they can be load via 'resume'

Any other information you'd like to share?

No response