aisman

Direct session 35, Step 1: Implement multi-user sessions, session issues rework, add-issues mode:
- Multi-user session & issue visibility
- Backend: include creator user info in session list/detail APIs
- Backend: restrict session continuation to creator
- Frontend: workflow tab ownership check dialog
- Session issues tab rework
- Rename step 'Issues created' tab to 'Session step issues'
- Rename session-level 'Issues created' tab to 'Session issues'
- Backend: session issues endpoint with touch count
- Frontend: session issues tab shows SessionIssue records with touch count display
- Frontend: session issues dirty marking on output file processing
- Add issues to session mode
- Render hidden add-issue checkboxes with data-id on all issue renders
- SCSS rules for add-issue-mode body class
- Session detail button row with 'Add issues' button
- Add-issue mode switching (body class, alert, button states)
- Add-issue mode state management and checkbox sync
- Session issues list live updates during add-issue mode
- Backend: bulk add/remove SessionIssue records
- Confirm/Cancel add-issue mode with save/restore logic
- Update help pages for session issues and add-issues mode