feat: Add task deletion with shift+click auto-confirm

- Add deleteTask tRPC mutation (repo already had delete method)
- Add X button to TaskRow, hidden until hover, with confirmation dialog
- Shift+click bypasses confirmation for fast bulk deletion
- Invalidates listInitiativeTasks on success
- Document shift+click pattern in CLAUDE.md as standard for destructive actions

docs/server-api.md

@@ -78,6 +78,7 @@ Each procedure uses `require*Repository(ctx)` helpers that throw `TRPCError(INTE
 | listInitiativeTasks | query | All tasks for initiative |
 | listPhaseTasks | query | All tasks for phase |
 | listPendingApprovals | query | Tasks with status=pending_approval |
+| deleteTask | mutation | Delete a task by ID |
 | approveTask | mutation | Approve and complete task |
 
 ### Initiatives