v0.56.0

Added

• Sketch strokes: draw in the Scene view and hand the line to the
  agent. The context bar's new "Sketch" menu (and an "Agent Sketch"
  toolbar overlay in the Scene view) arms one of two modes; a left drag
  then draws a stroke (S1, S2, ...) that becomes a context chip carrying
  the world-space points, and the new read-only uap_stroke_list tool
  (module markers) returns every stroke as JSON -- points, per-point
  normals and the objects a surface stroke was drawn on, length, closed
  flag, bounds and the sketch plane. Plane mode draws on a plane at
  a depth you choose: the Scene view shows the plane's section contour
  on every mesh it cuts, a depth-tested grid patch under the cursor, and
  a readout of the depth and of how far the surface under the cursor is
  in front of or behind the plane; the wheel and [ ] move the depth,
  F snaps it to the surface under the cursor, X/Y/Z lock a world-axis
  plane, C returns to camera-facing, Shift draws a straight line.
  Surface mode draws on the mesh surface under the cursor. Strokes
  are Scene-view overlays only (also drawn into camera-mode screenshots),
  survive a domain reload, and vanish on scene change or Play Mode; the
  chip's X, the "N scene markers" chip's clear button, or Esc handles
  them like pins. Design note
  docs/design-notes/2026-09-17-scene-sketch-strokes.md.