Feature(LMM/Auth) : Support for GHE - Copilot for Github Enterprise

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Problem:

LLM providers during netclaw init for Github/copilot currently only supports Github device login flow and not GHE / Enterprise endpoints:

Motivation: Some enterprise users are restricted to GHE for AI access.

Proposed Solution:
Add an env option to use GHE (default: github.com).
Environment support for copilot cli - the defaults for GHE could be mirrored:

GHE_HOST=my-company-tenant.ghe.com
GH_HOST=my-company-tenant.ghe.com
COPILOT_GH_HOST=my-company-tenant.ghe.com
GITHUB_SERVER_URL=https://my-company-tenant.ghe.com
GITHUB_API_URL=https://api.my-company-tenant.ghe.com

Example gh login for GHE:

gh auth login --hostname **my-company-tenant**.ghe.com

which will use the device browser login:

https://**my-company-tenant**.ghe.com/login/device

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Thanks for the link @Aaronontheweb, ill try test my company GHE_HOST + GITHUB_API_URL as the auth endpoint and report back the findings & possible PR.

[Aaronontheweb]

resolved via #1509