Time Series: Properly store and restore selection

[janezd]

Issue

Fixes #290.

Description of changes

selection was not stored properly (now it is) and it was cleared when reinitializing the model (now it's not; I block the signals from selection model).

As a bonus, migration takes care of existing workflows, which should now with correct selections.

Includes

• Code changes
• Tests

[Copilot]

Pull Request Overview

This PR addresses Issue #290 by properly storing and restoring the selection in time series workflows while preventing unintended signal clearing during model reinitialization. Key changes include:

• Introducing a new setting, pending_selection, to hold saved selections
• Updating the selection update logic in _selection_changed and set_data
• Adding tests to validate selection restoration and migration

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
orangecontrib/timeseries/widgets/tests/test_owdifference.py	Added tests for restored selection and settings migration
orangecontrib/timeseries/widgets/owdifference.py	Revised selection handling to use pending_selection and updated migration logic

Comments suppressed due to low confidence (1)

orangecontrib/timeseries/widgets/owdifference.py:108

• [nitpick] The simultaneous assignment to both 'pending_selection' and 'selection' could be confusing; add a clarifying comment or consider refactoring to clearly differentiate their roles if they are intended to serve separate purposes.

self.pending_selection = self.selection = [