feat(wasm): load_bytes — parse CAD documents from memory

Add a cross-platform `io::load_bytes(name, bytes)` that parses DWG/DXF
from an in-memory buffer via acadrust's stream readers (Cursor), picking
the format from the name's extension. This is the foundation for opening
files on the web, where the browser delivers bytes rather than a path.

Native keeps the streaming `load_file` (lower memory on large drawings);
both share the post-load fixups. Builds on native and wasm.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/io/mod.rs

@@ -86,6 +86,37 @@ pub async fn open_path_with_phase(
     Ok((name, path, doc, caches))
 }
 
+/// Parse a CAD document from in-memory bytes, choosing the format from
+/// `name`'s extension. Used by the web build, where files arrive as bytes from
+/// a browser file picker (no filesystem path). Shares the post-load fixups with
+/// [`load_file`]; raster-image path resolution is skipped (there is no sibling
+/// directory to search on the web).
+pub fn load_bytes(name: &str, bytes: Vec<u8>) -> Result<CadDocument, String> {
+    use std::io::Cursor;
+    let ext = name.rsplit('.').next().unwrap_or_default().to_lowercase();
+    match ext.as_str() {
+        "dwg" => {
+            let mut doc = DwgReader::from_stream(Cursor::new(bytes))
+                .read()
+                .map_err(|e| e.to_string())?;
+            fix_viewport_status_flags(&mut doc);
+            fix_current_style_names(&mut doc);
+            Ok(doc)
+        }
+        "dxf" => {
+            let mut doc = DxfReader::from_reader(Cursor::new(bytes))
+                .map_err(|e| e.to_string())?
+                .read()
+                .map_err(|e| e.to_string())?;
+            fix_dxf_dimension_rotations(&mut doc);
+            fix_viewport_status_flags(&mut doc);
+            fix_current_style_names(&mut doc);
+            Ok(doc)
+        }
+        _ => Err(format!("Unsupported file format: .{ext}")),
+    }
+}
+
 /// Load a DWG or DXF file directly from a path (auto-detect by extension).
 pub fn load_file(path: &Path) -> Result<CadDocument, String> {
     let ext = path