Reads two env vars: MSENS_FORCE_ALL (global truthy → force everything) and
MSENS_FORCE (comma-separated target names). Notebooks pass the result to
write_manifest() force= and/or use it to gate their own expensive rebuild.
Reads two env vars: MSENS_FORCE_ALL (global truthy → force everything) and
MSENS_FORCE (comma-separated target names). Notebooks pass the result to
write_manifest() force= and/or use it to gate their own expensive rebuild.