What a clever workaround! Trying it... and... nuts, no dice.
HOWEVER!
I installed the free version of Construct, and noticed that the plugins folder had all kinds of subfolders in it, whereas the Steam version's folder (Steam\steamapps\common\Construct2\exporters\html5\plugins) was completely empty. So I decided to dig around, and found that Steam installs two separate versions of C2, a 32-bit and a 64-bit version (no biggie, C2 is tiny). I went into my 64-bit folder and found the usual C2 folder structure, complete with a loaded plugins folder. I placed the scml folder in there (which is located at
D:\Program Files (x86)\Steam\steamapps\common\Construct2\Construct2-Win64\exporters\html5\plugins
by the way), and VOILA! Working Spriter. Thanks for the idea guidance! And, of course, the great program.
Updating thread for searchability, since I'm guessing that other plugins will have this problem, and the manual doesn't seem to address this. Tagging Ashley re: an update to the manual entry on plugins would be very handy. Sorry if that's not cool!