Let reviews see low-confidence suggestions and rebase preview applies

A low-confidence answer was discarded inside Classify, so Analyse showed
the row as unchanged instead of a reviewable suggestion; the fallback
decision moves to the import path, which keeps the merchant link and the
recorded confidence. ApplyPreview now rebases onto the current journal:
unrelated commits during a minutes-long paced run no longer invalidate
the review, only an edit to a selected transaction itself conflicts, and
applied changes are pruned so the rest stay appliable.

internal/classification/client_test.go

@@ -438,7 +438,7 @@ func TestConfiguredPrivateNamesAndIdentifiersRedactWithoutRemovingPayee(t *testi
 	}
 }
 
-func TestLowConfidenceKeepsMerchantAndTagsButUsesFallback(t *testing.T) {
+func TestLowConfidenceKeepsProposalAndRecordsConfidence(t *testing.T) {
 	f, d := fixture()
 	c := mockClient(t, func(w http.ResponseWriter, r *http.Request) {
 		reply(w, `{"merchant_id":"mer_coffee","new_merchant":null,"category_id":"cat_food","tag_ids":["tag_daily"],"confidence":"low"}`)
@@ -447,11 +447,13 @@ func TestLowConfidenceKeepsMerchantAndTagsButUsesFallback(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if p.Enrichment.CategoryID != domain.ExpenseFallback ||
+	// Review flows need the model's suggestion; discarding it is the import
+	// path's decision, not the client's.
+	if p.Enrichment.CategoryID != "cat_food" ||
 		p.Enrichment.MerchantID != "mer_coffee" ||
 		!reflect.DeepEqual(p.Enrichment.TagIDs, []string{"tag_daily"}) ||
 		p.Enrichment.Classification.Confidence != "low" {
-		t.Fatalf("low-confidence proposal was not preserved safely: %+v", p)
+		t.Fatalf("low-confidence proposal was not preserved: %+v", p)
 	}
 }