Derive a runtime-bin PATH prefix (MOSAIC_RUNTIME_BIN override, then
npm-prefix/bin, then ~/.npm-global/bin / ~/.local/bin) and bake it
into the tmux pane command as `export PATH="<prefix>:${PATH}"; exec
<cmd>` so the runtime binary (mosaic/pi/codex) is always found in a
login+non-interactive pane shell that does not source ~/.bashrc.
Using `exec` makes the runtime the pane foreground process, eliminating
the DRIFT false-positive in `mosaic fleet ps`.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RMoEx7hfdFGjUiCHuN1RRi
