TL;DR - seems to have resolved itself. The fluid was power steering fluid, I believe.
I still had bit of spray at the beginning of the trip. A quick inspection of the engine bay by everyone came to the conclusion that it was power steering fluid from when I removed the PS pump to replace the A/C compressor. We agreed that it was either: residual fluid that'd seeped into various crevice's and was leaking back out as the engine bay warmed up, or I didn't get the banjo bolt quite tight enough on the pressurized power steering line. By the end of the trip - having done nothing - no more fluid was being thrown around. I still plan to tighten the banjo bolt slightly.
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