Build ghost shows valid on factory bibs, but fails
Building placement is shown as valid while hovering over the bib of a factory, but fails when attempting to place. Should show as blocked in ghost mode.

This appears to affect:
- Tank Foundry (Somewhat)
- Gunship Plant (Somewhat)
- Rover Assembly (Somewhat)
- Shieldbot Factory
- Cloakbot Factory
- Hovercraft Platform
Does not affect:
- Amphbot Factory
- Jumpbot Factory
- Spider Factory
- Airplane Plant
- Shipyard
And also affects trying to place a factory when the bib it would create would overlap an already built structure.
Also the ghost has a green footprint if you try to put a Lotus inside an active Hovercraft Platform (for example). This probably needs engine work as I don't think we can change the placement mask in lua without creating LOS hax.
Engine ticket requesting proper tools to approach this. beyond-all-reason/spring#1303