Is your feature request related to a problem? Please describe.

As far as I know this is a known feature/exploit in the community, but I was unable to find any issues/PRs on it, so I'll describe it in some detail. As of now having a reach weapon and being able to climb to a roof trivializes many locations, including those that are supposed to be a challenge to a player (at least judging by the rewards). The strategy is as follows: equip a reach weapon, climb to a roof, attract zombies, wait till they approach, hold 'f' until everyone is dead, wait to regain stamina, rinse and repeat. Example: I've just cleared out a FEMA camp by a newly created char with mediocre combat abilities (8 str, 8 dex, 2 melee, 2 dodge, 2 piercing, no combat traits - in fact, no traits at all), several copper spears and a stepladder (both items are an easy craft even in the very beginning).

Describe the solution you'd like

Expand the grab attack to also grab reach attack weapons: if a zombie that has a GRAB as a possible attack gets hit with a reach attack from a higher z-level, it has a chance to perform a counter (similar to the ZAPBACK functionality). Depending on how deadly you want it to be, the counter itself can be pulling the weapon out of the player's hands (similar to technician's PULL_METAL_WEAPON, but not restricted by material) or outright pulling the character off the roof (as with wrestler's RANGED_PULL). The former is a nuisance, but, IMO, still enough to clamp on the exploit, unless one brings scores of spears, while the latter is, in effect, a death sentence.
Reality-wise: zombies grabbing at the character should be just as happy to grab at any object shoved at them; grabbing a long spear is relatively easy; once grabbed and pulled forward, the spear owner can try to wrestle it free if on the level ground and not high above the opponent, but if caught on the ledge, their choices are basically to let go of the weapon or fall down.

Additional context

No response