Counter-Strike 2's responsive smoke is cool and all, but can GoldSRC do it?

Yes. Yes, it can.

Alrighty, source code is now public:
https://github.com/Admer456/halflife-smoke
GitHub - Admer456/halflife-smoke: HL1 but with CS2-style interactive smoke

HL1 but with CS2-style interactive smoke. Contribute to Admer456/halflife-smoke development by creating an account on GitHub.

GitHub