When CCS launches Claude with CLAUDE_CONFIG_DIR pointing to the isolated
instance path, agent team teammates spawned via tmux split-window don't
inherit it because tmux creates new panes from its own session environment.
This causes teammates to use ~/.claude/ instead of ~/.ccs/instances/{profile}/,
creating a split-brain in shared state (tasks, teams, mailbox).
Sets key CCS env vars in the tmux session environment via `tmux setenv` so
all new panes inherit the correct config directory.
