Cargo: codec 3ec70a2, kernel e710727, graph 338a973

The codec keeps dynamic-block, associative and material records intact on
DWG save (strict readers rejected re-saved drawings at BLOCKSCALEACTION,
associative action bodies and MATERIAL records). A checker material
texture no longer rewrites the native map source, so a map with a
procedural texture counts as content whatever its source says.

Valuable parts of #1671 (with opencadcodec#100): measured on 235 sample
drawings re-saved after an edit, a strict reader now rejects 4 instead
of 7; the remaining 4 are R14/R2000 tables, which the PR codec also
fails.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/scene/model/material_model.rs

@@ -187,8 +187,9 @@ impl MeshTextureMap {
     }
 
     pub fn has_content(&self) -> bool {
-        (self.source == 1 && !self.file_name.trim().is_empty())
-            || (self.source == 2 && self.procedural)
+        // A procedural texture counts whatever the native source says: a
+        // checker asset attaches its texture without rewriting the source.
+        (self.source == 1 && !self.file_name.trim().is_empty()) || self.procedural
     }
 }