feat: add conversation deletion endpoint (soft delete) [LET-7286] (#9230)

* feat: add conversation deletion endpoint (soft delete) [LET-7286]

- Add DELETE /conversations/{conversation_id} endpoint
- Filter soft-deleted conversations from list operations
- Add check_is_deleted=True to update/delete operations

Co-authored-by: Sarah Wooders <sarahwooders@users.noreply.github.com>

🤖 Generated with [Letta Code](https://letta.com)

Co-Authored-By: Letta <noreply@letta.com>

* feat: add tests, update SDK and stainless for delete conversation

- Add 5 integration tests for DELETE conversation endpoint
- Run stage-api to regenerate OpenAPI spec and SDK
- Add delete method to conversations in stainless.yml

Co-authored-by: Sarah Wooders <sarahwooders@users.noreply.github.com>

🤖 Generated with [Letta Code](https://letta.com)

Co-Authored-By: Letta <noreply@letta.com>

* test: add manager-level tests for conversation soft delete [LET-7286]

- test_delete_conversation_removes_from_list
- test_delete_conversation_double_delete_raises
- test_update_deleted_conversation_raises
- test_delete_conversation_excluded_from_summary_search

🤖 Generated with [Letta Code](https://letta.com)

Co-Authored-By: Letta <noreply@letta.com>

---------

Co-authored-by: letta-code <248085862+letta-code@users.noreply.github.com>
Co-authored-by: Letta <noreply@letta.com>
Co-authored-by: Sarah Wooders <sarahwooders@gmail.com>

tests/integration_test_conversations_sdk.py

@@ -567,6 +567,94 @@ class TestConversationsSDK:
         assert first_message_id not in [m.id for m in messages_after]
 
 
+class TestConversationDelete:
+    """Tests for the conversation delete endpoint."""
+
+    def test_delete_conversation(self, client: Letta, agent, server_url: str):
+        """Test soft deleting a conversation."""
+        # Create a conversation
+        conversation = client.conversations.create(agent_id=agent.id)
+        assert conversation.id is not None
+
+        # Delete it via REST endpoint
+        response = requests.delete(
+            f"{server_url}/v1/conversations/{conversation.id}",
+        )
+        assert response.status_code == 200, f"Expected 200, got {response.status_code}: {response.text}"
+
+        # Verify it's no longer accessible
+        response = requests.get(
+            f"{server_url}/v1/conversations/{conversation.id}",
+        )
+        assert response.status_code == 404, f"Expected 404 for deleted conversation, got {response.status_code}"
+
+    def test_delete_conversation_removes_from_list(self, client: Letta, agent, server_url: str):
+        """Test that deleted conversations don't appear in list."""
+        # Create two conversations
+        conv1 = client.conversations.create(agent_id=agent.id)
+        conv2 = client.conversations.create(agent_id=agent.id)
+
+        # Verify both appear in list
+        conversations = client.conversations.list(agent_id=agent.id)
+        conv_ids = [c.id for c in conversations]
+        assert conv1.id in conv_ids
+        assert conv2.id in conv_ids
+
+        # Delete one
+        response = requests.delete(
+            f"{server_url}/v1/conversations/{conv1.id}",
+        )
+        assert response.status_code == 200
+
+        # Verify only the non-deleted one appears in list
+        conversations = client.conversations.list(agent_id=agent.id)
+        conv_ids = [c.id for c in conversations]
+        assert conv1.id not in conv_ids, "Deleted conversation should not appear in list"
+        assert conv2.id in conv_ids, "Non-deleted conversation should still appear"
+
+    def test_delete_conversation_not_found(self, client: Letta, agent, server_url: str):
+        """Test that deleting a non-existent conversation returns 404."""
+        fake_id = "conv-00000000-0000-0000-0000-000000000000"
+        response = requests.delete(
+            f"{server_url}/v1/conversations/{fake_id}",
+        )
+        assert response.status_code == 404
+
+    def test_delete_conversation_double_delete(self, client: Letta, agent, server_url: str):
+        """Test that deleting an already-deleted conversation returns 404."""
+        # Create and delete a conversation
+        conversation = client.conversations.create(agent_id=agent.id)
+
+        # First delete should succeed
+        response = requests.delete(
+            f"{server_url}/v1/conversations/{conversation.id}",
+        )
+        assert response.status_code == 200
+
+        # Second delete should return 404
+        response = requests.delete(
+            f"{server_url}/v1/conversations/{conversation.id}",
+        )
+        assert response.status_code == 404, "Double delete should return 404"
+
+    def test_update_deleted_conversation_fails(self, client: Letta, agent, server_url: str):
+        """Test that updating a deleted conversation returns 404."""
+        # Create and delete a conversation
+        conversation = client.conversations.create(agent_id=agent.id)
+
+        response = requests.delete(
+            f"{server_url}/v1/conversations/{conversation.id}",
+        )
+        assert response.status_code == 200
+
+        # Try to update the deleted conversation
+        response = requests.patch(
+            f"{server_url}/v1/conversations/{conversation.id}",
+            json={"summary": "Updated summary"},
+        )
+        assert response.status_code == 404, "Updating deleted conversation should return 404"
+
+
 class TestConversationCompact:
     """Tests for the conversation compact (summarization) endpoint."""