Make config default tests deterministic by clearing env vars and reloading module

Agent-Logs-Url: https://github.com/CyberSecDef/NovelForge/sessions/f855c09b-c821-4cac-a8ba-53e869009651

Co-authored-by: CyberSecDef <17597068+CyberSecDef@users.noreply.github.com>

Author: Copilot

tests/test_length_enforcement.py

@@ -259,13 +259,25 @@ def mock_llm(msgs, action=""):
 class TestLengthEnforcementConfig:
     """Verify config constants exist and have sensible defaults."""
 
-    def test_chapter_min_length_pct_default(self):
+    def test_chapter_min_length_pct_default(self, monkeypatch):
+        import importlib
         import novelforge.config as cfg
-        assert cfg.CHAPTER_MIN_LENGTH_PCT == 85
-
-    def test_max_expansion_attempts_default(self):
+        monkeypatch.delenv("CHAPTER_MIN_LENGTH_PCT", raising=False)
+        importlib.reload(cfg)
+        try:
+            assert cfg.CHAPTER_MIN_LENGTH_PCT == 85
+        finally:
+            importlib.reload(cfg)
+
+    def test_max_expansion_attempts_default(self, monkeypatch):
+        import importlib
         import novelforge.config as cfg
-        assert cfg.MAX_EXPANSION_ATTEMPTS == 2
+        monkeypatch.delenv("MAX_EXPANSION_ATTEMPTS", raising=False)
+        importlib.reload(cfg)
+        try:
+            assert cfg.MAX_EXPANSION_ATTEMPTS == 2
+        finally:
+            importlib.reload(cfg)
 
     def test_chapter_min_length_pct_in_all(self):
         import novelforge.config as cfg