feat(tui): add usage overlay and sidebar for displaying usage statistics and tasks

feat(tui): implement status bar with connection and turn state indicators
feat(tui): create workflow panel for agent status and progress visualization
feat(web): introduce web frontend interface with static file serving
feat(ws): add WebSocket interface for real-time communication and session management

apps/infrastructure/src/subagent/event.rs

@@ -0,0 +1,27 @@
+//! Subagent event types — events emitted during subagent execution.
+
+/// Events emitted by a running subagent.
+#[derive(Debug, Clone)]
+pub enum SubagentEvent {
+    Started {
+        agent_id: String,
+        directive: String,
+    },
+    ToolCall {
+        agent_id: String,
+        tool_name: String,
+    },
+    ToolResult {
+        agent_id: String,
+        tool_name: String,
+        output: String,
+    },
+    Completed {
+        agent_id: String,
+        output: String,
+    },
+    Failed {
+        agent_id: String,
+        error: String,
+    },
+}