Confusing comment on a JS branch instruction

https://github.com/jart/sectorlisp/blob/fc6fa331d23807cae685a1cfbcb3e2955e2aa08f/sectorlisp.S#L113-L114

This says:

* "set sf=1 if cons"
* `js` (jump if sign bit set)
* "jump if not cons"

The `js` jump actually jumps if `sf=1` so there is a contradiction here. I don't understand the code enough to determine which comment is wrong.

Read sectorlisp.S at lines 113-114 and inspect the surrounding boot-sector branch logic. Verify the condition used by the js instruction against the nearby cons test, then update the contradictory comment so it accurately describes the code. Done means the comments consistently explain whether the branch is taken for cons or non-cons values.

Written by the indexing model from the issue text.