feat(KB-640): add role editing UI and restore KB task prefix

- Add inline role editing to AgentListModal with clickable role icons
- Add handleRoleChange and handleRoleKeyDown handlers for role updates
- Persist view toggle (board/list) with localStorage alongside role editing
- Restore task prefix from FN back to KB for generated task IDs
- Restore branch naming from fusion/ back to kb/ for task branches
- Update branch name references in executor, merger, scheduler, and CLI
- Add touch gesture detection support to TaskCard component
- Update worktree grouping labels to use KB prefix

packages/engine/src/merger.ts

@@ -538,7 +538,7 @@ export async function aiMergeTask(
     );
   }
 
-  const branch = `fusion/${taskId.toLowerCase()}`;
+  const branch = `kb/${taskId.toLowerCase()}`;
   const worktreePath = task.worktree;
   const result: MergeResult = {
     task,