feat(commands): add ARCHIVE / ETRANSMIT (folder package)

Package the drawing plus its referenced files (xrefs + raster images)
into a sibling "<name>_archive" folder via std::fs, reusing the
existing block_records / entities iterators. COMMANDS.md: 217/262.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/commands/mod.rs

@@ -344,6 +344,8 @@ inventory::submit!(crate::command::CommandRegistration {
         "XOPEN",
         "REGION",
         "REG",
+        "ARCHIVE",
+        "ETRANSMIT",
         // Slice/section + interference + press-pull/thicken + 3D transforms + wall/pyramid.
         "SLICE",
         "SL",