How about websites just straight up aren't allowed to physically hurt me, by default?

Web sites aren’t made for just you. If images from your screen are causing you issues, that is a you / your device problem, not a web site problem.

I agree, it's not a web site problem. It's a web standards problem that it's possible for web sites to do that.

Note the spec does recommend providing a user option: https://drafts.csswg.org/css-color-hdr-1/#a11y

You asked “which web browsers have a setting to tone map HDR images such that they look like SDR images?”; I answered. Were you not actually looking for a solution?

I was looking for a setting, not a hack.