A recompiled type no longer loads its build twice

Since this morning's compilation fix, a NodeType compiled on the same server that serves it loaded each new build twice — once from the compiler's output and once from the assembly store's copy of the same bytes — and an open instance of the type kept both copies alive until it closed. The extra copy did not grow with further recompiles, but every build a live instance was running sat in memory twice. A request for the store's copy now reuses the copy already loaded, so each build is loaded once, and a recompile releases it as before.

Details: One build at two paths is ONE generation.