Sheet sets: Place on Sheet, sheet view menus, block lists, missing status, field refresh

Model Views lists named model views and places them on the current sheet
(xref, viewport, paper-space named view, view label with navigation
fields, sheet view record); sheet view rows get Display, Rename & Renumber
View, Set category, Place Callout Block and Place View Label Block; the
View Category dialog's Add Blocks opens List of Blocks / Select Block; a
sheet whose relative path is gone shows missing; sheet set fields store
their values when a set changes; named views keep their centre relative to
the target. Codec pin moves to the revision with these field helpers.

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=29aff7e#29aff7e8e6f4669cd1f41fc82d39521127c07d03"
+source = "git+https://github.com/ramox81/cadcodec.git?rev=1ace49e#1ace49ea940cd4e1337befac1004e57a7d36015b"
 dependencies = [
  "ahash 0.8.12",
  "anyhow",