Feature #5753 - Autosave for ifc files

Implemented as described in #5753, with two options:
- A nag dialog with save or cancel options.
- An autosaved file.

Settings are in preference to activate the feature (default: off), the period before prompting/saving,
and choosing between the two methods.

Prevent the autosave file being added to the recent files list when the user opens the original, but selects to open the autosaved version.

black/ruff

This commit was created using AI assistance. Cursor for the initial code, then Grok and I fixing all the errors
that Cursor made. Finally Copilot did a code review.

I have reviewed and tested the code, and I understand it, and it works and does not introduce any obvious bugs.

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Grok
Co-authored-by: Cursor

src/bonsai/test/bim/module/project/test_autosave.py

@@ -0,0 +1,68 @@
+# Bonsai - OpenBIM Blender Add-on
+# Copyright (C) 2026
+#
+# This file is part of Bonsai.
+#
+# Bonsai is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Bonsai is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was generated with the assistance of an AI coding tool.
+
+import os
+import time
+from pathlib import Path
+
+import pytest
+
+from bonsai.tool.autosave import AUTOSAVED_SUFFIX, AUTOSAVING_SUFFIX, Autosave
+
+pytestmark = pytest.mark.project
+
+
+class TestAutosavePaths:
+    def test_get_paths_for_ifc_file(self):
+        main_path, autosaving_path, autosaved_path = Autosave.get_paths("/tmp/myfile.ifc")
+        assert main_path == Path("/tmp/myfile.ifc")
+        assert autosaving_path == Path(f"/tmp/myfile{AUTOSAVING_SUFFIX}")
+        assert autosaved_path == Path(f"/tmp/myfile{AUTOSAVED_SUFFIX}")
+
+    def test_get_newer_autosaved_path_when_missing(self, tmp_path):
+        ifc_path = tmp_path / "myfile.ifc"
+        ifc_path.write_text("ifc")
+        assert Autosave.get_newer_autosaved_path(ifc_path) is None
+
+    def test_get_newer_autosaved_path_when_older(self, tmp_path):
+        ifc_path = tmp_path / "myfile.ifc"
+        autosaved_path = tmp_path / f"myfile{AUTOSAVED_SUFFIX}"
+        ifc_path.write_text("ifc")
+        autosaved_path.write_text("autosaved")
+        past = time.time() - 10
+        os.utime(ifc_path, (past, past))
+        os.utime(autosaved_path, (time.time(), time.time()))
+        assert Autosave.get_newer_autosaved_path(ifc_path) == autosaved_path.as_posix()
+
+    def test_get_newer_autosaved_path_when_not_newer(self, tmp_path):
+        ifc_path = tmp_path / "myfile.ifc"
+        autosaved_path = tmp_path / f"myfile{AUTOSAVED_SUFFIX}"
+        ifc_path.write_text("ifc")
+        autosaved_path.write_text("autosaved")
+        now = time.time()
+        os.utime(ifc_path, (now, now))
+        past = now - 10
+        os.utime(autosaved_path, (past, past))
+        assert Autosave.get_newer_autosaved_path(ifc_path) is None
+
+    def test_get_newer_autosaved_path_ignores_non_ifc(self, tmp_path):
+        path = tmp_path / "myfile.ifczip"
+        path.write_text("zip")
+        assert Autosave.get_newer_autosaved_path(path) is None