fix(v2): support nested repository paths

backend/src/backup_tool/repository.py

@@ -64,7 +64,13 @@ def _canonical_json(payload: dict[str, object]) -> str:
 
 
 def _assert_capacity(settings: Settings, root: Path) -> None:
-    usage = shutil.disk_usage(root)
+    capacity_root = root
+    while not capacity_root.exists():
+        parent = capacity_root.parent
+        if parent == capacity_root:
+            raise RepositoryError("repository root is unreadable")
+        capacity_root = parent
+    usage = shutil.disk_usage(capacity_root)
     free_percent = usage.free * 100 / usage.total
     if usage.free < settings.min_free_bytes or free_percent < settings.min_free_percent:
         raise RepositoryError("repository root does not meet minimum free capacity")

tests/integration/test_repository_safety.py

@@ -61,6 +61,13 @@ def test_initialization_rejects_symlinked_destination_component(tmp_path: Path)
         initialize(settings, "linked/child", "none", "none")
 
 
+def test_initialization_supports_not_yet_created_nested_path(tmp_path: Path) -> None:
+    settings = settings_for(tmp_path)
+    result = initialize(settings, "nested/main", "none", "none")
+    assert result.root == settings.repository_roots[0] / "nested" / "main"
+    assert (result.root / "repository.json").is_file()
+
+
 @pytest.mark.parametrize(
     ("minimum", "usage"),
     [
@@ -79,7 +86,9 @@ def test_initialization_rejects_insufficient_capacity(
         initialize(settings, "main", "none", "none")
 
 
-def test_initialization_emits_complete_repository_protocol_metadata(tmp_path: Path) -> None:
+def test_initialization_emits_complete_repository_protocol_metadata(
+    tmp_path: Path,
+) -> None:
     result = initialize(settings_for(tmp_path), "main", "none", "none")
     try:
         payload = json.loads((result.root / "repository.json").read_text(encoding="utf-8"))