feat(backend): Implement discussion branching and take promotion

tests/test_discussion_takes.py

@@ -0,0 +1,50 @@
+import unittest
+from src import project_manager
+
+class TestDiscussionTakes(unittest.TestCase):
+ def setUp(self):
+  self.project_dict = project_manager.default_project("test_branching")
+  # Populate initial history in 'main'
+  self.project_dict["discussion"]["discussions"]["main"]["history"] = [
+   "User: Message 0",
+   "AI: Response 0",
+   "User: Message 1",
+   "AI: Response 1",
+   "User: Message 2"
+  ]
+
+ def test_branch_discussion_creates_new_take(self):
+  """Verify that branch_discussion copies history up to index and sets active."""
+  source_id = "main"
+  new_id = "take_1"
+  message_index = 1
+  
+  # This will fail with AttributeError until implemented in project_manager.py
+  project_manager.branch_discussion(self.project_dict, source_id, new_id, message_index)
+  
+  # Asserts
+  self.assertIn(new_id, self.project_dict["discussion"]["discussions"])
+  new_history = self.project_dict["discussion"]["discussions"][new_id]["history"]
+  self.assertEqual(len(new_history), 2)
+  self.assertEqual(new_history[0], "User: Message 0")
+  self.assertEqual(new_history[1], "AI: Response 0")
+  self.assertEqual(self.project_dict["discussion"]["active"], new_id)
+
+ def test_promote_take_renames_discussion(self):
+  """Verify that promote_take renames a discussion key."""
+  take_id = "take_experimental"
+  self.project_dict["discussion"]["discussions"][take_id] = project_manager.default_discussion()
+  self.project_dict["discussion"]["discussions"][take_id]["history"] = ["User: Experimental"]
+  
+  new_id = "feature_refined"
+  
+  # This will fail with AttributeError until implemented in project_manager.py
+  project_manager.promote_take(self.project_dict, take_id, new_id)
+  
+  # Asserts
+  self.assertNotIn(take_id, self.project_dict["discussion"]["discussions"])
+  self.assertIn(new_id, self.project_dict["discussion"]["discussions"])
+  self.assertEqual(self.project_dict["discussion"]["discussions"][new_id]["history"], ["User: Experimental"])
+
+if __name__ == "__main__":
+ unittest.main()