- New shaper.go: ShapeText() returns ShapedText with measured width +
stored PathSpec + BitmapsCall, DrawShapedText() draws with zero shaper calls
- drawStatusBar: ShapeText for filename + right icons, positions from widths
- drawBottomBar: ShapeText for cursor/bytepos/wrap, positions by alignment
- No separate measureText helper: ShapeText.Width provides measurements
- StatusBar uses IconLeft/IconRow string slices for icon configuration
- BottomBar uses BarAlignment enum for item positioning
