GitHub CLI auth hardened; setup works behind firewalls

Patch Changes

• 23843e9: Read the GitHub CLI auth token by invoking gh directly instead of through a shell. The shell wrapper (cmd.exe /d /s /c on Windows) caused endpoint protection tools such as Microsoft Defender for Endpoint to raise a "Suspicious Node.js process behavior" alert during ctx7 setup.
• c82cc8a: Fix ctx7 setup skill install failing with "fetch failed" when the GitHub git tree API (api.github.com) is blocked or unreachable. Skill download now falls back to fetching the single SKILL.md directly from raw.githubusercontent.com — the URL the docs API already resolves — so setup succeeds in environments where only the docs/raw hosts are reachable.
• 1c081df: Improve query prompts so agents request relevant library documentation instead of passing the task to complete.