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/lib/adapters/btmsg-bridge.ts

@@ -0,0 +1,72 @@
+/**
+ * btmsg bridge — reads btmsg SQLite database for agent notifications.
+ * Used by GroupAgentsPanel to show unread counts and agent statuses.
+ * Polls the database periodically for new messages.
+ */
+
+import { invoke } from '@tauri-apps/api/core';
+
+export interface BtmsgAgent {
+  id: string;
+  name: string;
+  role: string;
+  group_id: string;
+  tier: number;
+  model: string | null;
+  status: string;
+  unread_count: number;
+}
+
+export interface BtmsgMessage {
+  id: string;
+  from_agent: string;
+  to_agent: string;
+  content: string;
+  read: boolean;
+  reply_to: string | null;
+  created_at: string;
+  sender_name?: string;
+  sender_role?: string;
+}
+
+/**
+ * Get all agents in a group with their unread counts.
+ */
+export async function getGroupAgents(groupId: string): Promise<BtmsgAgent[]> {
+  return invoke('btmsg_get_agents', { groupId });
+}
+
+/**
+ * Get unread message count for an agent.
+ */
+export async function getUnreadCount(agentId: string): Promise<number> {
+  return invoke('btmsg_unread_count', { agentId });
+}
+
+/**
+ * Get unread messages for an agent.
+ */
+export async function getUnreadMessages(agentId: string): Promise<BtmsgMessage[]> {
+  return invoke('btmsg_unread_messages', { agentId });
+}
+
+/**
+ * Get conversation history between two agents.
+ */
+export async function getHistory(agentId: string, otherId: string, limit: number = 20): Promise<BtmsgMessage[]> {
+  return invoke('btmsg_history', { agentId, otherId, limit });
+}
+
+/**
+ * Send a message from one agent to another.
+ */
+export async function sendMessage(fromAgent: string, toAgent: string, content: string): Promise<string> {
+  return invoke('btmsg_send', { fromAgent, toAgent, content });
+}
+
+/**
+ * Update agent status (active/sleeping/stopped).
+ */
+export async function setAgentStatus(agentId: string, status: string): Promise<void> {
+  return invoke('btmsg_set_status', { agentId, status });
+}