Implement the REQ-UI-MULTI-SELECTION addition: the selected building
panel now shows the total placement cost of a multi-selection, counting
only player-placeable buildings (HQ and defence stations excluded).
Construction sites are charged their type's full cost.
Add a shared BuildingsConfig::findBuildingDef accessor and reuse it in
BlueprintPanel to remove the duplicated by-type lookup loops.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DZR44tA8sn4dPqDzAVXyps
Implement REQ-UI-BUILD-TOOLTIP and REQ-MOD-UI-MODULE-TOOLTIP: an optional
tooltip string on BuildingDef and ModuleDef, parsed from buildings.toml and
modules.toml and shown as the build/module button's hover tooltip. Omitted
when unset. Author descriptions for all buildings and modules in the app
config, and extend ConfigLoaderTest to cover the optional field.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DZR44tA8sn4dPqDzAVXyps
