Built Junk Metal Floors don't have roofs

### Describe the bug

After building a junk metal floor, my housebase doesn't have roofs. This is after reloading the game.

### Attach save file

[Uploading Brockport-trimmed.tar.gz…]()

### Steps to reproduce

1. Build junk metal roof
2. Climb up
3. Notice no roof!

### Expected behavior

The description says 'A simple floor and roof of junk metal', and it's quite expensive to make. So it should have a roof.

### Screenshots


Aftershock: Exoplanet. The junk metal floors are the ones I built up myself.

One z-level up, the roofs that _look_ like junk metal are just the tileset using the same sprite for normal, unbuildable metal rooftops. The actual constructed junk metal floors have no matching roof.

### Versions and configuration

- OS: Windows
- OS Version: 10.0.19045.3930 (22H2)
- Game Version: 0f39e72 [64-bit]
- Graphics Version: Tiles
- Game Language: System language []
- Mods loaded: [
Dark Days Ahead [dda],
Disable NPC Needs [no_npc_food],
Portal Storms Ignore NPCs [personal_portal_storms],
Slowdown Fungal Growth [no_fungal_growth],
Aftershock [aftershock],
Aftershock: Exoplanet [aftershock_exoplanet],
My mod [my_mod]
]

### Additional context

I have a personal mod that only changes a handful of items and their recipes, and which should not cause this conflict.

Reproduce the issue by building a junk metal floor, climbing up, and reloading the supplied save if available. Trace the definition and construction behavior for junk metal floors and compare it with the roof behavior described in the issue. Done means the constructed floor provides the expected roof after reloading, with a regression check for the reported steps.

Written by the indexing model from the issue text.