Add disconnect/uninstall for persistent sessions

- Server: Add DELETE /api/sessions/:id endpoint to disconnect agents
- Server: SessionManager.disconnect_session() sends Disconnect message
- Agent: Handle ADMIN_DISCONNECT to trigger uninstall
- Agent: Add startup::uninstall() to remove from startup and schedule exe deletion
- Dashboard: Add Disconnect button in Access tab machine details
- Dashboard: Add Chat button for persistent sessions

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

server/src/main.rs

@@ -81,6 +81,7 @@ async fn main() -> Result<()> {
         // REST API - Sessions
         .route("/api/sessions", get(list_sessions))
         .route("/api/sessions/:id", get(get_session))
+        .route("/api/sessions/:id", axum::routing::delete(disconnect_session))
         
         // HTML page routes (clean URLs)
         .route("/login", get(serve_login))
@@ -178,6 +179,23 @@ async fn get_session(
     Ok(Json(api::SessionInfo::from(session)))
 }
 
+async fn disconnect_session(
+    State(state): State<AppState>,
+    Path(id): Path<String>,
+) -> impl IntoResponse {
+    let session_id = match uuid::Uuid::parse_str(&id) {
+        Ok(id) => id,
+        Err(_) => return (StatusCode::BAD_REQUEST, "Invalid session ID"),
+    };
+
+    if state.sessions.disconnect_session(session_id, "Disconnected by administrator").await {
+        info!("Session {} disconnected by admin", session_id);
+        (StatusCode::OK, "Session disconnected")
+    } else {
+        (StatusCode::NOT_FOUND, "Session not found")
+    }
+}
+
 // Static page handlers
 async fn serve_login() -> impl IntoResponse {
     match tokio::fs::read_to_string("static/login.html").await {

server/src/session/mod.rs

@@ -134,6 +134,32 @@ impl SessionManager {
         }
     }
 
+    /// Disconnect a session by sending a disconnect message to the agent
+    /// Returns true if the message was sent successfully
+    pub async fn disconnect_session(&self, session_id: SessionId, reason: &str) -> bool {
+        let sessions = self.sessions.read().await;
+        if let Some(session_data) = sessions.get(&session_id) {
+            // Create disconnect message
+            use crate::proto;
+            use prost::Message;
+
+            let disconnect_msg = proto::Message {
+                payload: Some(proto::message::Payload::Disconnect(proto::Disconnect {
+                    reason: reason.to_string(),
+                })),
+            };
+
+            let mut buf = Vec::new();
+            if disconnect_msg.encode(&mut buf).is_ok() {
+                // Send via input channel (will be forwarded to agent's WebSocket)
+                if session_data.input_tx.send(buf).await.is_ok() {
+                    return true;
+                }
+            }
+        }
+        false
+    }
+
     /// List all active sessions
     pub async fn list_sessions(&self) -> Vec<Session> {
         let sessions = self.sessions.read().await;