v0.5.1

[0.5.1] - 2026-07-07

A feature-bearing patch over the 0.5.0 crate rename: a new volume-rendering
widget, a toolbar restructure across the image-widget family, and the profile
overlay drawn on the image. Also the first cross-platform CI (Linux / macOS /
Windows), which surfaced and fixed a Direct3D-12 shader-portability bug. rsdm
and adl2rsdm are re-released in lockstep (no functional change beyond an
internal lint cleanup).

Added — rsplot

• VolumeRaycaster — an interactive GPU direct-volume-rendering widget.
  Ray-marches a (depth, height, width) RGBA8 volume in a fragment shader
  (shaders/volume_raycaster.wgsl): a full-screen triangle un-projects each
  pixel through the inverse camera matrix, slab-tests the volume box, and
  front-to-back alpha-composites samples of a 3-D texture straight into egui's
  render pass (premultiplied-alpha blend, no offscreen target or depth buffer).
  Orbit / pan / wheel-zoom reuse the existing Camera + OrbitDrag / PanDrag
  interaction state machines. Transfer knobs: set_alpha_scale (global opacity),
  set_steps (samples per ray), set_cull_floor (skip near-transparent
  samples). Unlike ScalarFieldView (iso-surface geometry), this renders the
  volume itself — every voxel's colour and opacity contribute along the ray.
  Naga-validated headlessly plus an egui_kittest wgpu render test (opaque
  volume ⇒ visible colour, transparent volume ⇒ nothing).
• Compact plot control toolbar. The Plot2D control toolbar now renders
  compact by default — the essential buttons (reset zoom, box-zoom / pan modes,
  invert Y, keep-aspect) stay in the row and everything else folds into a single
  ⋯ overflow menu, so the toolbar stays one line and the plot keeps its
  height. Toggle with Plot::set_toolbar_compact (toolbar_compact to read).
• Shared control toolbar on ImageView, ImageStack, and CompareImages.
  All three now surface the standard silx plot controls above their own rows,
  matching the rest of the image-widget family (previously reachable only on the
  bare inner plot).
• ImageView image controls as detached settings windows. The image-specific
  controls (interp / agg / alpha / profile / mask) are now toolbar buttons that
  each open their own detached settings window, matching silx's toolbar-action /
  dock-widget layout instead of inline combos and sliders. The colorbar stays a
  plain toggle.
• Profile overlay drawn on the image. The profile ROI and its width band are
  now drawn directly on the image while a profile tool is active.

Fixed — rsplot

• Curve rendering no longer fails on Windows / Direct3D-12. The curve
  fragment shader ended in a function-terminal discard, which naga's HLSL
  backend emits as a path with no return value; the D3D12 FXC compiler rejects
  it (X3507, "not all control paths return a value"), so create_render_pipeline
  for the curve pipeline — and every curve / scatter draw — failed on Windows.
  Vulkan and Metal tolerate it, so it was invisible until cross-platform CI. A
  trailing unreachable return keeps the shader portable.
• The plot no longer zooms while a profile drag positions the ROI. A drag
  that places or resizes a profile ROI is consumed by the profile tool instead
  of also driving a box zoom.