The honcho check_fn only checked runtime session state, which isn't
set until the agent initializes. At banner time, honcho tools showed
as red/disabled even when properly configured.
Now checks configuration (enabled + api_key/base_url) as a fallback
when the session context isn't active yet. Fast path (session active)
unchanged; slow path (config check) only runs at banner time.
Adds 4 tests covering: session active, configured but no session,
not configured, and import failure graceful fallback.
Closes#1843.
c774833667