unify(worldbuilder): Add Generals compatibility prerequisites

[OmarAglan]

What changed

• Added Generals support for WorldBuilder polygon-trigger layers, selection state, and render state.
• Added the map trigger version needed to serialize layer names.
• Exposed the ThingTemplate vision, ambient-sound, and weapon metadata used by the unified editor.
• Registered the ambient-sound map-object keys used by WorldBuilder.

Why

Zero Hour's richer WorldBuilder implementation depends on engine metadata that Generals did not expose. Keeping these compatibility changes in a separate prerequisite PR makes the later editor merge reviewable without hiding engine changes inside it.

Impact

This PR changes only Generals engine compatibility surfaces. It does not merge or move WorldBuilder sources.

Validation

• git diff --check
• Clean working tree
• Exactly one commit relative to main

Stack

1 of 3. Merge this PR first.