Adds UiMeter, the horizontal vital-bar widget for the D.2b retail-look
UI toolkit. Solid-color fill for Spec 1; the retail orb sprite + scissor
crop path is reserved for a later sub-phase. Five unit tests (1 Fact +
4 Theory) cover half-fill geometry and clamping at -1/0/1/2 fractions.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Implements the retail floating-window bevel as a UiPanel subclass using
RetailChromeSprites: 4 tiled edges + 4 stretched corners + tiled center fill,
matching the 8-piece border layout confirmed by the D.2b Step-0 prove-out.
Resolver delegate keeps GL out of unit tests. Geometry verified by
ComputeFrameRects_PlacesCornersEdgesAndCenter (1/1 pass).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>