buckshot homing to marines

## Testmerges
#11075: 'Ticket Panel (Adminhelps & Mentorhelps)' by GeneriedJenelle at commit 4ad8d0cf87
#12174: 'Yautja Armor Sets' by realforest2001 at commit 90c66798ed
#10414: 'Port: Harm Intent uses Auto-Fire instead of PB' by MistChristmas at commit d44502d495
#11161: 'Gas trap buff & neuro smoke tweaks' by Diegoflores31 at commit 92b29e6eb0
#12361: 'pride scarfs in loadout' by Detective-Google at commit 6ddcf88cb8
#12140: 'Tyrargo Rift - Various Alterations' by Steelpoint at commit 13c4e6de58
#12434: 'Attempts to fix runaway explosion recursion' by Drulikar at commit 51f684daed
#12486: 'Revert "Optimize flamer fire spread"' by hry-gh at commit a860f57e6f
#10696: '[code bounty] Sentinel rework' by cuberound at commit 84e7e38047
#12500: 'Test: Reduce bitfield2list maximum' by MistChristmas at commit 97b591ae3a
#12502: 'hotfix for #12501 blood decal issue' by Detective-Google at commit 411b4c7f1c

## Round ID
34929

## Description of the bug
buckshot will occasionally drift perfectly towards marines
https://streamable.com/ft81dy
ive had this happen to me quite consistently when using a shotgun as of recent, i will comment clips as i get them

## What's the difference with what should have happened?
it shouldnt do that

## How do we reproduce this bug?
1) Get a buckshot shotgun and stand next to a marine or xeno, try a couple different positions (i.e. the position of the smartgunner and warrior relative to me in the clip provided)
2) Fire at the xeno (try sprite clicking, tile clicking, whatever)
3) Repeat a few times; this feels random but also guaranteed, so you'll need to do it a few times in testing to really see its effect.

## Attached logs
```
N/A
```

## Additional details
- Author: Stakeyng
- Admin: the goodwheatley
- Note: None

Reproduce the issue using the listed shotgun, target positions, and both sprite- and tile-clicking methods, while comparing buckshot aimed at a xeno near marines. The issue names no files or tests, so first locate the buckshot firing and projectile-movement entry points in the repository. Done means repeated shots no longer drift toward nearby marines and the behavior is covered by a reliable reproduction or regression test.

Written by the indexing model from the issue text.