Fix viewer-only installs registering as agents

Previously, any installation with the protocol handler registered
would default to running as an agent. This caused admin/technician
machines (viewer-only) to appear in the sessions list.

Changes:
- Add Config::has_agent_config() to check for explicit agent config
- Only run as agent when: explicit 'agent' command, support code
  provided, OR agent config file exists
- Viewer-only installs (protocol handler but no config) now exit
  silently when launched without arguments

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

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

agent/src/main.rs

@@ -221,14 +221,23 @@ fn main() -> Result<()> {
             if let Some(code) = cli.support_code {
                 run_agent_mode(Some(code))
             } else {
-                // No args: check if protocol handler is installed
-                // If not, run install mode (user likely downloaded from web)
+                // No args: check what mode to run
                 if !install::is_protocol_handler_registered() {
+                    // Protocol handler not registered - user likely downloaded from web
+                    // Run installer to set up protocol handler
                     info!("Protocol handler not registered, running installer");
                     run_install(false)
-                } else {
-                    // Protocol handler exists, run as agent
+                } else if config::Config::has_agent_config() {
+                    // Protocol handler exists AND agent config exists
+                    // This is an agent installation - run as agent
+                    info!("Agent config found, running as agent");
                     run_agent_mode(None)
+                } else {
+                    // Protocol handler exists but NO agent config
+                    // This is a viewer-only installation - just exit silently
+                    // The protocol handler will launch the viewer when needed
+                    info!("Viewer-only installation, exiting (use 'guruconnect agent' to run as agent)");
+                    Ok(())
                 }
             }
         }