GHES: gh aw audit should auto-detect GHES and set GH_HOST

[lpcox]

Problem

gh aw audit <run-id> fails on GHES repositories because it does not detect the GHES host. The command tries to query github.com instead of the GHES instance.

Users must manually prefix with GH_HOST=<ghes-host>:

# Fails
gh aw audit 22039091

# Works
GH_HOST=contoso-aw.ghe.com gh aw audit 22039091

Proposal

• Auto-detect GHES from the current repo remote (same way gh CLI does for other commands)
• Set GH_HOST internally when GHES is detected
• Include Copilot licensing status in audit output when engine: copilot is used (e.g., "Copilot seat: assigned / not assigned / unknown")

Related

• add-wizard and add --create-pull-request fail to create PR on GitHub Enterprise Server repositories #20875 — Wizard also fails on GHES for same reason

[pelikhan]

@copilot review add-wizard and apply auto-detection to all commands.