fix(sunshine): use Intel rendering and recover remote Niri sessions (#268)

- render Niri on the Intel iGPU while retaining NVIDIA-connected physical outputs
- encode Sunshine streams with Intel VAAPI and wait for a Niri output before startup
- load VKMS persistently for headless sessions and configure `Virtual-1` at 2560x1600@60
- let Moonlight request the stream bitrate instead of enforcing a 20 Mbps host cap
- remove unsupported Dynamic Boost and global NVIDIA session overrides
- grant Sunshine access to virtual input devices
- add a Nushell recovery helper that starts a temporary greetd/Niri session from SSH
- identify and safely replace normal, standalone, or previous transient Niri sessions
- launch the transient service in the background and verify greetd, Niri, and Sunshine before returning
- ignore local `.worktrees` directories and keep eval regression coverage focused on structural behavior

hosts/idols-ai/niri-hardware.kdl

@@ -1,4 +1,10 @@
 // running `niri msg outputs` to find outputs
+debug {
+    // Keep desktop rendering and ordinary applications on the Intel iGPU.
+    // Physical outputs remain on the NVIDIA GPU and use cross-GPU scanout.
+    render-drm-device "/dev/dri/by-path/pci-0000:00:02.0-render"
+}
+
 output "DP-1" {
     // Uncomment this line to disable this output.
     // off
@@ -37,6 +43,16 @@ output "HDMI-A-2" {
     position x=2560 y=0 // on the right of DP-2
 }
 
+output "Virtual-1" {
+    // Created by vkms in hardware-intel.nix. Sunshine captures this output when
+    // the NVIDIA-attached physical monitors are off. It remains available in
+    // normal physical sessions, with minor idle GPU and framebuffer overhead.
+    scale 1
+    transform "normal"
+    mode "2560x1600@60"
+    position x=0 y=0
+}
+
 // ============= Named Workspaces =============
 workspace "4entertainment" { open-on-output "DP-1"; }
 workspace "2browser" { open-on-output "DP-1"; }