Best as I can see, we currently use the gulp (and npm) infrastructure for two reasons: * it compiles SCSS to CSS, does some further jiggling, and copies the result to the two target projects * it copies the JS* to the two target projects *) it does _not_ compile TS to JS: the MSBuild toolchain does that instead. This works, but it's kind of an ugly and brittle fit. We might want to move to things like `BuildWebCompiler`.