feat(agents): role-specific tabs + bttask Tauri backend

- TaskBoardTab: kanban board (5 columns, CRUD, comments, 5s poll) for Manager
- ArchitectureTab: PlantUML viewer/editor (4 templates, plantuml.com) for Architect
- TestingTab: Selenium screenshots + test file discovery for Tester
- bttask.rs: Rust backend (list, create, update_status, delete, comments)
- bttask-bridge.ts: TypeScript IPC adapter
- ProjectBox: conditional role tabs (isAgent && agentRole), PERSISTED-LAZY

v2/src/lib/adapters/bttask-bridge.ts

@@ -0,0 +1,57 @@
+// bttask Bridge — Tauri IPC adapter for task board
+
+import { invoke } from '@tauri-apps/api/core';
+
+export interface Task {
+  id: string;
+  title: string;
+  description: string;
+  status: 'todo' | 'progress' | 'review' | 'done' | 'blocked';
+  priority: 'low' | 'medium' | 'high' | 'critical';
+  assignedTo: string | null;
+  createdBy: string;
+  groupId: string;
+  parentTaskId: string | null;
+  sortOrder: number;
+  createdAt: string;
+  updatedAt: string;
+}
+
+export interface TaskComment {
+  id: string;
+  taskId: string;
+  agentId: string;
+  content: string;
+  createdAt: string;
+}
+
+export async function listTasks(groupId: string): Promise<Task[]> {
+  return invoke<Task[]>('bttask_list', { groupId });
+}
+
+export async function getTaskComments(taskId: string): Promise<TaskComment[]> {
+  return invoke<TaskComment[]>('bttask_comments', { taskId });
+}
+
+export async function updateTaskStatus(taskId: string, status: string): Promise<void> {
+  return invoke('bttask_update_status', { taskId, status });
+}
+
+export async function addTaskComment(taskId: string, agentId: string, content: string): Promise<string> {
+  return invoke<string>('bttask_add_comment', { taskId, agentId, content });
+}
+
+export async function createTask(
+  title: string,
+  description: string,
+  priority: string,
+  groupId: string,
+  createdBy: string,
+  assignedTo?: string,
+): Promise<string> {
+  return invoke<string>('bttask_create', { title, description, priority, groupId, createdBy, assignedTo });
+}
+
+export async function deleteTask(taskId: string): Promise<void> {
+  return invoke('bttask_delete', { taskId });
+}