- Update buildAllAgents() to scan all directories in .bmad/
- Update checkBuildStatus() to check all modules
- Update listAvailableAgents() to list all modules
- Auto-detect .bmad or bmad folder name
- Skip special directories (_cfg, docs)
This makes 'bmad build --all' discover custom modules (custom/, hde/, etc.)
and builds their agents automatically, matching the behavior of the fixed
install/compile workflow.
Related to #990