Fixed nearby structures collapsing when digging terrain, plus other bugs.

● Fixed building structures near destroyed terrain dropping/disappearing. Now they only drop when fully unsupported from below.

● Fixed "Quick Move to Backpack" not merging with existing stacks when both backpack and belt were full.

● Fixed item tooltips not showing after disassembling an item until hovering over another.

● Weapon parts can now be right-clicked to disassemble into resources, saving backpack space.