Strip \r characters from list-panes output to handle Windows-style line
endings. Also relax field count check from 9 to 8 to handle cases where
pane_title is empty or missing, which caused the parser to drop pane
rows and fail to determine the main pane in single-pane sessions.
Fixes#2241
- Account for tmux pane dividers (1 char) in all size calculations
- Reduce MIN_PANE_WIDTH from 53 to 52 to fit 2 columns in standard terminals
- Fix enforceMainPaneWidth to use (windowWidth - divider) / 2
- Add virtual mainPane handling for close-spawn eviction loop
- Add comprehensive decision-engine tests (23 test cases)