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-tauri/src/commands/bttask.rs

@@ -0,0 +1,38 @@
+use crate::bttask;
+
+#[tauri::command]
+pub fn bttask_list(group_id: String) -> Result<Vec<bttask::Task>, String> {
+    bttask::list_tasks(&group_id)
+}
+
+#[tauri::command]
+pub fn bttask_comments(task_id: String) -> Result<Vec<bttask::TaskComment>, String> {
+    bttask::task_comments(&task_id)
+}
+
+#[tauri::command]
+pub fn bttask_update_status(task_id: String, status: String) -> Result<(), String> {
+    bttask::update_task_status(&task_id, &status)
+}
+
+#[tauri::command]
+pub fn bttask_add_comment(task_id: String, agent_id: String, content: String) -> Result<String, String> {
+    bttask::add_comment(&task_id, &agent_id, &content)
+}
+
+#[tauri::command]
+pub fn bttask_create(
+    title: String,
+    description: String,
+    priority: String,
+    group_id: String,
+    created_by: String,
+    assigned_to: Option<String>,
+) -> Result<String, String> {
+    bttask::create_task(&title, &description, &priority, &group_id, &created_by, assigned_to.as_deref())
+}
+
+#[tauri::command]
+pub fn bttask_delete(task_id: String) -> Result<(), String> {
+    bttask::delete_task(&task_id)
+}

v2/src-tauri/src/commands/mod.rs

@@ -10,3 +10,4 @@ pub mod files;
 pub mod remote;
 pub mod misc;
 pub mod btmsg;
+pub mod bttask;