Extract isCmuxCompatEnvironment to shared module and fix interactive_bash to resolve cmux executables with the __tmux-compat prefix, matching all other tmux command paths in the codebase.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent) Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>