skip tests whose optional dependency is not installed

With pywikidiff2 and mediawiki-utilities no longer installed by default,
the tests covering --diff, -p wikidiff2, and -p legacy cannot run on a
base install. Mark them so a base install reports skips rather than
failures, and keep the markers in wikiq_test_utils.py so all three test
modules share one definition of what each feature needs.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
(cherry picked from commit 59d5a9d46a04320bad5d81e0edf5ecd11f9c2a9b)

test/test_resume.py

@@ -15,6 +15,7 @@ from wikiq_test_utils import (
     TEST_OUTPUT_DIR,
     WIKIQ,
     WikiqTester,
+    requires_pywikidiff2,
 )
 
 
@@ -65,6 +66,7 @@ def test_resume():
     assert_frame_equal(df_full, df_resumed)
 
 
+@requires_pywikidiff2
 def test_resume_with_diff():
     """Test that --resume correctly computes diff values after resume.
 
@@ -305,6 +307,7 @@ def test_resume_data_equivalence():
     assert_frame_equal(df_full, df_resumed)
 
 
+@requires_pywikidiff2
 def test_resume_with_persistence():
     """Test that --resume correctly handles persistence state after resume.
 
@@ -403,6 +406,7 @@ def test_resume_corrupted_jsonl_last_line():
     assert_frame_equal(df_full, df_resumed)
 
 
+@requires_pywikidiff2
 def test_resume_diff_persistence_combined():
     """Test that --resume correctly handles both diff and persistence state together.
 
@@ -448,6 +452,7 @@ def test_resume_diff_persistence_combined():
     assert_frame_equal(df_full, df_resumed)
 
 
+@requires_pywikidiff2
 def test_resume_mid_page():
     """Test resume from the middle of a page with many revisions.
 
@@ -501,6 +506,7 @@ def test_resume_mid_page():
     assert_frame_equal(df_full, df_resumed)
 
 
+@requires_pywikidiff2
 def test_resume_page_boundary():
     """Test resume at the exact start of a new page.