Dragging furniture causes movement over dragged furniture

### Describe the bug

Grabbing a small boulder, then moving in opposite direction of the boulder (dragging it behind you) causes messages of moving over the boulder, meaning the character is slowed down as if walking over the boulder while dragging it.

### Steps to reproduce

1. Grab small boulder
2. Move into opposite direction from the boulder
3. Observe message log saying "moving off of this small boulder is slow" every step

### Expected behavior

Dragging furniture with grab should not cause character to move onto said furniture every step.

### Screenshots

_No response_

### Versions and configuration

- OS: Windows
- OS Version: 10.0 2004
- Game Version: 6ca3ef2 [64-bit]
- Graphics Version: Tiles
- Game Language: System language []
- Mods loaded: [
Dark Days Ahead [dda],
Disable NPC Needs [no_npc_food],
No Fungal Growth [no_fungal_growth],
Bionic Professions [package_bionic_professions]
]

### Additional context

_No response_

Start by reproducing the issue with a small boulder: grab it, move in the opposite direction, and confirm the repeated slow-movement messages. Trace the movement and furniture-grabbing entry points involved, then verify that dragging the furniture no longer treats the character as moving onto it or applies its slowdown on each step.

Written by the indexing model from the issue text.