Two tasks: window-restore.py + unit tests, then the niri config declaration,
bind rewiring and install.sh symlink. Script precedes config so Mod+Shift+M is
never wired to a missing script.
Plan code verified by extracting both blocks and running the test suite against
the script: 18/18 pass, and the step-2 failure mode is confirmed.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>