I just found a workaround. I post here to save someone else my public embarrassment.
1. Make a List View Layout
2. Add a MERGE FIELD
3. Apply a button action to that merge field
4. Create a hover state on the merge field
5. Switch to browse mode
6. Roll your cursor over the field to see it change, regardless of record focus.
Not sure why this doesn't work with regular fields (yes, the field is shut off from entry in Browse mode, and has a button action applied to it), and does work with a Merge Field, but that fact is immaterial to my solution.