Theme (scenes/ui/medieval_theme.gd):
- Procedural builder for an app-wide Theme: parchment buttons on
dark-wood border, tan panels, ink text, gold focus ring.
- Applied on the root Window in Main._ready, with a tree-walk that
re-seeds every CanvasLayer's topmost Control (CanvasLayer
interrupts the root-Window theme cascade in Godot 4).
- Late-mounting popups + modals get themed via a child_entered_tree
hook on each CanvasLayer.
Build drawer thumbnails (scenes/ui/build_drawer_thumb.gd):
- New BuildDrawerThumb Control that dispatches on tool_id and draws
a recognisable silhouette of the entity each tool builds. 17 tools
covered: chop/mine/dig_grave/no_roof (Designate), stone+wood walls,
wood+stone floors, door, crate, bed, torch, 5 workbenches
(Carpenter/Smelter/Millstone/Hearth/Cremation Pyre), stockpile,
graveyard.
- Replaces the flat ColorRect placeholder. _add_tool_btn signature
changed from (label, color, callback) to (label, tool_id, callback).
