Sheet sets: fields evaluated when a sheet opens; VIEW WINDOW

- A drawing's sheet set fields are refreshed when it opens with sets loaded.
- VIEW WINDOW <name> <x1,y1> <x2,y2> saves the plan view of a window.
- opencadcodec: block-attribute fields use their block reference's layout.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Cargo.lock

@@ -4206,7 +4206,7 @@ dependencies = [
 [[package]]
 name = "opencadcodec"
 version = "0.5.5"
-source = "git+https://github.com/ramox81/cadcodec.git?rev=1ace49e#1ace49ea940cd4e1337befac1004e57a7d36015b"
+source = "git+https://github.com/ramox81/cadcodec.git?rev=5f4653a#5f4653ada2008eb0db5917abb0cb68f489edecc0"
 dependencies = [
  "ahash 0.8.12",
  "anyhow",