So I pulled my trusty Kindle Fire out of my pocket, only to find slugs racing across the edge:
Turns out those are leaves of the Sedum Morganianum, a.k.a. Lamb’s Tail, plant next to the window behind my desk:
I’d been leaning in there past the plant stand to swap cables for the new portrait monitor, brushed against the plant, and knocked some leaves into my pocket. The bare sections on the right side are entirely my fault, although not entirely during this incident; the leaves seem perfectly willing to fall off during a harsh glance.
You can find more than you probably want to know about the care & feeding of Sedum Morganianum, some of which suggests that those tendrils have reached pretty nearly their maximum length. If past experience is any guide, the heavy glazed ceramic pot will eventually overbalance and auto-trim the stems to a length suitable for replanting in a new & intact pot.