Search the library in the import section

The search shows the matches from a story site that Bindery does not track yet. The button that lists every such book stays.

tests/test_deliver.py

@@ -151,9 +151,18 @@ def test_library_candidates_and_search(fake):
             "formats": ["epub"],
         }
     ]
+    # A search shows only the matches from a story site.
+    fake.books.append(FakeBook(2, "uuid-2", "Test Novel", publisher="A Publisher", epub=b"x"))
+    fake.books.append(FakeBook(4, "uuid-4", "Other Story", publisher="www.royalroad.com", epub=b"x"))
+    assert [b["id"] for b in orchestrator.search_library("test")] == [1, 2]
+    assert orchestrator.library_candidates("test") == candidates
+    assert [b["id"] for b in orchestrator.library_candidates("story")] == [1, 4]
+    assert orchestrator.library_candidates("nothing") == []
+    assert orchestrator.library_candidates(" ") == []
     story_id = add_story()
     orchestrator.link_story(story_id, "uuid-1")
-    assert orchestrator.library_candidates() == []
+    assert [b["id"] for b in orchestrator.library_candidates()] == [4]
+    assert orchestrator.library_candidates("test") == []
     assert orchestrator.search_library("test")[0]["tracked_as"] == "Test Story"
     with pytest.raises(KeyError):
         orchestrator.link_story(story_id, "uuid-nope")