Unblock CI import sorting

Ruff fails the clean GitHub runner on an unsorted import block in the vector retrieval tests. Normalizing the imports keeps the new CI workflow deterministic without changing test behavior.

Constraint: CI runs Ruff from a clean runner with import sorting enabled
Rejected: Relax Ruff import sorting | the repository already selects I rules and the fix is mechanical
Confidence: high
Scope-risk: narrow
Reversibility: clean
Tested: ruff check --no-cache src/ tests/; mypy src/; pytest -q --cov=govintel --cov-report=term-missing --cov-fail-under=90; git diff --check
Not-tested: GitHub Actions result after this push

Author: sahaavi

tests/test_retrieval/test_vector.py

@@ -7,9 +7,9 @@
 from typing import Any
 
 import pytest
-from govintel.retrieval.vector import ChromaVectorStore, PineconeVectorStore
 
 from govintel.ingestion.embedder import EmbeddingModel, embed_and_load
+from govintel.retrieval.vector import ChromaVectorStore, PineconeVectorStore
 
 
 def test_chroma_vector_store_returns_ranked_results(