Also group assignments in the same way as notes

build.py

@@ -75,13 +75,29 @@ def scan_shared() -> list[Section]:
 
     assignments_dir = SHARED_DIR / "assignments"
     if assignments_dir.exists():
-        zip_name = "assignments.zip"
-        create_zip(assignments_dir, ZIPS_DIR / zip_name)
-        sections.append(Section(
-            title="Assignments",
-            zip_url=f"zips/{zip_name}",
-            files=list_files(assignments_dir),
-        ))
+        subdirs = sorted(
+            d for d in assignments_dir.iterdir()
+            if d.is_dir() and should_include(d)
+        )
+        if subdirs:
+            subsections = []
+            for subdir in subdirs:
+                zip_name = f"assignments-{subdir.name}.zip"
+                create_zip(subdir, ZIPS_DIR / zip_name)
+                subsections.append(SubSection(
+                    name=subdir.name,
+                    zip_url=f"zips/{zip_name}",
+                    files=list_files(subdir),
+                ))
+            sections.append(Section(title="Assignments", subsections=subsections))
+        else:
+            zip_name = "assignments.zip"
+            create_zip(assignments_dir, ZIPS_DIR / zip_name)
+            sections.append(Section(
+                title="Assignments",
+                zip_url=f"zips/{zip_name}",
+                files=list_files(assignments_dir),
+            ))
 
     notes_dir = SHARED_DIR / "notes-and-examples"
     if notes_dir.exists():