9646bc1c4c
Both `_new_agent_flow` (bringup) and `_stop_bottle_flow`
(teardown) were doing the same five-step dance: open the log
path, mkdir parents, empty the file, ensure the right pane is
tailing it, redirect fd 2 to the same file. Extract into a
context manager:
with _route_op_to_right_pane(tmux_state, slug, log_name) as routed:
if routed:
<run op>
Yields True when routing succeeded (fd 2 redirected, pane
tailing), False on fallback conditions (not in tmux, no
tmux_state, or tmux failed to spawn a pane). The fallback
paths still differ between callers — bringup follows up
with `_attach_in_tmux`, teardown does the curses-endwin
compose-down — so the helper stops at "is stderr routed
or not" and lets callers branch from there. Net diff:
~60 lines deleted, the routing-to-right-pane concept now
lives in one place.