windows-rdp: Add option to open in native RDP desktop client

[DevelopmentCats]

Feature Request

The windows-rdp module (powered by Devolutions Gateway) currently only provides a web-based RDP client. It would be useful to have an option to launch the native RDP desktop client (e.g., Microsoft Remote Desktop, mstsc.exe) directly.

Use Case

Some users prefer the native RDP experience for:

• Better performance and responsiveness
• Full clipboard integration
• Multi-monitor support
• Familiar keyboard shortcuts
• Integration with local RDP credential managers

Proposed Implementation

Add a variable to optionally create a coder_app with external = true that generates an .rdp file or uses an rdp:// URI scheme to launch the native client.

variable "enable_native_rdp" {
  type        = bool
  description = "Add an app button to open in the native RDP desktop client."
  default     = false
}

This could work similarly to how local-windows-rdp handles native RDP connections, but integrated into the main windows-rdp module as an optional feature.

Related

• coder/local-windows-rdp module handles native RDP but is a separate module
• Consider whether these modules should be unified or if this should remain a separate concern

[linear-code]

ENG-3255