The gateway dispatcher captured kanban.auto_decompose ONCE at boot, so a user
who flipped it to false to STOP auto-decompose had no way to make that take
effect short of restarting the gateway. Reported (#49638): auto-decompose
created and launched tasks the user never intended (while they were still
typing the task description), and 'even Hermes Agent couldn't disable this
feature' — because the live config edit was silently ignored.
Auto-decompose is a safety toggle; turning it off must halt fan-out on the
next tick. The dispatcher now re-reads the flag (and auto_decompose_per_tick)
from config every tick via the extracted _resolve_auto_decompose_settings(),
which fails SAFE (disabled) on a config read error so a transient failure can
never re-enable a feature the user turned off.
Closes#49638.
