feat(block-editor): edit definition properties in the Properties panel

Add the no-selection Block section with annotation, orientation, scaling, exploding, units, description and hyperlink controls. Integrate definition edits with editor history, save checkpoints and discard, and keep staged text tied to its definition.

Persist annotation and hyperlink metadata on the block record, migrate legacy marker values on edit, and honor orientation and hyperlink descriptions during block creation. Cover native DWG/DXF roundtrips and replacement after reopening.

src/scene/mod.rs

@@ -7,6 +7,7 @@
 //   cache   — block-definition and property caches
 pub mod annotative;
 pub mod assoc_array;
+pub(crate) mod block_metadata;
 pub mod block_service;
 pub mod block_visibility;
 pub mod cache;