aisman

Session 72, Step 5: Diff direction fix, shortcut fixes, project switch, select button improvements, Up/Down traversal, story auto-update
- AIM-1084 Fix diff line alignment with empty placeholder lines
- AIM-1111 Global shortcuts F/R/I/S/W/T/1/2/3/4
- AIM-1142 Project-scoped localStorage for issues, sessions, and user stories
- AIM-1147 Select buttons UI: 'Select:' label, button group, rename Ready/Non-ready/All
- AIM-1148 Select issues: 'Last step' button with counter badge
- AIM-1149 Select issues buttons: Ctrl/Shift/Ctrl+Shift modifier key behaviors
- AIM-1151 Up/Down buttons: focus only, do not expand/collapse
- Auto-update story title from output file step.storyTitle
- Remove 'Unsaved changes' dialog when switching stories; save to localStorage with beforeunload guard
- sessionStepCount undefined — ensure always set when session detail loads