feat(orchestration): add bttask CLI + GroupAgentsPanel + btmsg Tauri bridge

Phase 2: bttask CLI (Python, SQLite) — task management with role-based
visibility. Kanban board view. Manager/Architect can create tasks,
Tier 2 agents receive tasks via btmsg only.

Phase 3: GroupAgentConfig in groups.json + Rust backend. GroupAgentsPanel
Svelte component above ProjectGrid with status dots, role icons,
unread badges, start/stop buttons.

Phase 4: btmsg Rust bridge (btmsg.rs) — read/write access to btmsg.db.
6 Tauri commands for agent status, messages, and history.
GroupAgentsPanel polls btmsg.db every 5s for live status updates.

v2/src-tauri/src/groups.rs

@@ -17,11 +17,30 @@ pub struct ProjectConfig {
     pub enabled: bool,
 }
 
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct GroupAgentConfig {
+    pub id: String,
+    pub name: String,
+    pub role: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub model: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub cwd: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub system_prompt: Option<String>,
+    pub enabled: bool,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub wake_interval_min: Option<u32>,
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct GroupConfig {
     pub id: String,
     pub name: String,
     pub projects: Vec<ProjectConfig>,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub agents: Vec<GroupAgentConfig>,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]