gpui_widgets defect fixes: menu checkmarks, dock ratios, meter orientation, CPU frames, drop-frame timecode

- 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)

crates/gpui_widgets/src/lib.rs

@@ -33,3 +33,48 @@ pub mod spinbox;
 pub mod theme;
 pub mod value;
 pub mod viewer;
+
+#[cfg(test)]
+mod tests {
+    use gpui::prelude::*;
+    use gpui::{AbsoluteLength, DefiniteLength, div, rems};
+
+    /// Fractional spacing helpers exist on the [`Styled`](gpui::Styled) trait
+    /// (via `gpui_macros::padding_style_methods!` / `margin_style_methods!`),
+    /// named after Tailwind's fractional scale: `0p5`, `1p5`, `2p5`, `3p5`
+    /// (i.e. 0.5/1.5/2.5/3.5 units of 4px = 2/6/10/14px).
+    ///
+    /// We deliberately do **not** add `_0_5`-style aliases (`py_0_5`,
+    /// `px_1_5`, ...): every fractional value they would name already exists
+    /// under the established `0p5`/`1p5`/`2p5`/`3p5` convention used
+    /// throughout gpui and gpui_widgets, and a second naming scheme for the
+    /// same helpers would only fragment the API surface. This test pins the
+    /// helpers (and their values) so a future refactor of the style macros
+    /// cannot silently drop them.
+    #[test]
+    fn fractional_spacing_helpers_exist() {
+        let mut padding = div().py_0p5().px_1p5();
+        assert_eq!(
+            padding.style().padding.top,
+            Some(DefiniteLength::Absolute(AbsoluteLength::Rems(rems(0.125))))
+        );
+        assert_eq!(
+            padding.style().padding.left,
+            Some(DefiniteLength::Absolute(AbsoluteLength::Rems(rems(0.375))))
+        );
+        assert_eq!(
+            padding.style().padding.right,
+            Some(DefiniteLength::Absolute(AbsoluteLength::Rems(rems(0.375))))
+        );
+
+        let mut margin = div().my_2p5().pt_3p5();
+        assert_eq!(
+            margin.style().margin.top,
+            Some(DefiniteLength::Absolute(AbsoluteLength::Rems(rems(0.625))).into())
+        );
+        assert_eq!(
+            margin.style().padding.top,
+            Some(DefiniteLength::Absolute(AbsoluteLength::Rems(rems(0.875))).into())
+        );
+    }
+}