Fix command executor timeout handling and add detached mode

- Add detached mode for long-running processes via detached=true config
- Fix process termination on timeout using process groups and kill -TERM/-KILL
- Remove double shell wrapping that was breaking command execution
- Track PIDs via wrapper script to enable proper process cleanup
- Flush port messages after timeout to prevent Tortoise MQTT errors
- Update example config to demonstrate detached command usage

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

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

server/systant.toml.example

@@ -102,6 +102,14 @@ command = "ping"
 allowed_params = ["-c", "4", "8.8.8.8", "google.com", "1.1.1.1"]
 description = "Network connectivity test"
 
+# Example of a detached command for long-running processes
+[[commands.available]]
+trigger = "start_app"
+command = "firefox"
+detached = true  # Don't wait for the process to exit, just launch it
+timeout = 5      # Timeout only applies to launching, not running
+description = "Start Firefox browser (detached)"
+
 [logging]
 level = "info"                                          # debug, info, warn, error
 log_config_changes = true