fix: reject duplicate bundle components

Assisted-by: GitHub Copilot (model: gpt-5.6-sol, autonomous)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: marcelsafin

src/specify_cli/bundler/models/manifest.py

@@ -192,9 +192,17 @@ def structural_errors(self) -> list[str]:
                 "(lowercase letters, digits, '.', '_', '-'; no path separators)."
             )
 
+        seen_components: set[tuple[str, str]] = set()
         for ref in self.components:
             if not ref.id:
                 errors.append(f"A {ref.kind[:-1]} entry is missing its 'id'.")
+            key = (ref.kind, ref.id)
+            if ref.id and key in seen_components:
+                errors.append(
+                    f"Duplicate {ref.kind[:-1]} '{ref.id}' in "
+                    f"'provides.{ref.kind}'."
+                )
+            seen_components.add(key)
             if ref.kind != "steps" and not ref.version:
                 errors.append(
                     f"{ref.kind[:-1]} '{ref.id or '<unknown>'}' must be pinned to a 'version'."

tests/contract/test_manifest_schema.py

@@ -127,6 +127,20 @@ def test_components_property_orders_by_kind():
     assert kinds == ["extensions", "presets", "steps", "workflows"]
 
 
+def test_duplicate_component_in_same_kind_is_rejected():
+    data = valid_manifest_dict()
+    data["provides"]["extensions"].append(
+        {"id": "ext-a", "version": "9.9.9"}
+    )
+
+    errors = BundleManifest.from_dict(data).structural_errors()
+
+    assert any(
+        "duplicate extension 'ext-a'" in error.lower()
+        for error in errors
+    )
+
+
 def test_string_tags_rejected_not_split_per_character():
     # A bare string would otherwise be iterated character-by-character; the
     # schema requires a list of strings.