feat(mcp): add Set-of-Marks grounding, regional framing, and 2-point image calibration

- Add Set-of-Marks (SoM) visual grounding (src/app/control/vision.rs):
  * Render high-contrast numbered badges on entity visual centroids in viewport captures
  * Project 3D entity bounds to 2D image coordinates with priority ranking (selected/size)
  * Return bidirectional grounding manifest (annotations / visible_entities) in capture and ocs_capture payloads mapping each badge to entity handle, layer, type, and world center

- Add regional viewport framing (src/app/control/mod.rs, src/mcp.rs):
  * Support view: region and bounds: [min_x, min_y, max_x, max_y] in capture and ocs_capture
  * Enable programmatic zoom and high-resolution inspection of specific rooms or local geometry

- Add 2-point raster image calibration (src/app/control/actions.rs, src/mcp_ops.rs):
  * Extend embed_image with optional source_points (pixel coords) and target_points (CAD coords)
  * Automatically calculate scale, world dimensions, and insertion origin at
  * Add unit test embed_image_calibrates_from_source_and_target_points

src/mcp_ops.rs

@@ -245,6 +245,8 @@ pub static EMBED_IMAGE: OpDef = OpDef {
         opt("at", Ty::Point, "Lower-left corner [x, y] or [x, y, z]."),
         opt("width", Ty::Num, "World width of the image."),
         opt("linked", Ty::Bool, "Store as path-linked RasterImage instead of embedded OLE2FRAME."),
+        opt("source_points", Ty::ArrayOf(&Ty::Point), "Pixel points in image [[px1,py1],[px2,py2]] for 2-point alignment."),
+        opt("target_points", Ty::ArrayOf(&Ty::Point), "CAD world points [[x1,y1],[x2,y2]] for 2-point alignment."),
     ],
     rules: &[],
     example: r#"{"op":"embed_image","path":"logo.png","at":[0,0]}"#,