- menu: add runtime set-checked path (MenuItem::set_checked/clear_checked,
Menu::set_item_checked recursive, MenuBar::set_item_checked)
- dock: Split now stores per-child ratios (sum 1.0) so 3+ panels on one
axis keep distinct sizes; resize_split_child adjusts a single boundary,
resize_split keeps its two-arg whole-share semantics; one handle per
boundary; DockLayoutState VERSION bumped to 2 for the new ratios field
- audio_meter: MeterOrientation::Vertical for the 26px transport strip,
segments lit bottom to top
- viewer: ViewerFrameSource::CpuFrame + set_cpu_frame (BGRA8 RenderImage
via the sprite atlas) for platforms without CVPixelBuffer
- timeline: TimeDisplay::TimecodeDropFrame (SMPTE drop-frame for NTSC
rates, non-drop fallback otherwise)
- gpui_widgets: regression test pinning the fractional spacing helpers
(py_0p5/py_1p5/py_2p5/py_3p5 already exist; no _0_5 aliases added)