fix: account pool auth in chat-only mode (Cursor CLI HOME isolation)

Pass pool config dir into chat-only env overrides and skip fake HOME when
using a pool: the agent CLI still resolves session auth via the real profile
for ask/--print, so a temp HOME caused spurious "Authentication required".

Tests cover getChatOnlyEnvOverrides; align workspace test defaultModel with
merged PR fixtures.

Made-with: Cursor