repo-hygiene: clean-build --apply runs dotnet clean then removes bin/obj wholesale — driver is pure overhead

[kyle-sexton]

Problem

clean-build.sh --apply runs the dotnet clean <solution> driver (full MSBuild evaluation, minutes on a large solution), then removes bin/obj wholesale anyway. The driver adds no removal coverage — everything it deletes lives under directories the globs remove — and dotnet clean itself re-creates obj/ evaluation artifacts.

Fix direction

Drop the driver from the rm path entirely, or gate it to a hypothetical mode where bin/obj are NOT bulk-removed. One walk + rm is strictly faster and equally complete.