use jovian-nixos + fixup niri display session handling

flake.lock

@@ -186,6 +186,27 @@
         "type": "github"
       }
     },
+    "jovian-nixos": {
+      "inputs": {
+        "nix-github-actions": "nix-github-actions",
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1763640802,
+        "narHash": "sha256-TAsO9p2cF/Wm6sYWPqvC/mBzMBzG119XLB6T0XwU2NU=",
+        "owner": "Jovian-Experiments",
+        "repo": "Jovian-NixOS",
+        "rev": "4b1c28efe3b31e00c427e651b398d8251dd29812",
+        "type": "github"
+      },
+      "original": {
+        "owner": "Jovian-Experiments",
+        "repo": "Jovian-NixOS",
+        "type": "github"
+      }
+    },
     "lanzaboote": {
       "inputs": {
         "crane": "crane",
@@ -309,6 +330,28 @@
         "type": "github"
       }
     },
+    "nix-github-actions": {
+      "inputs": {
+        "nixpkgs": [
+          "jovian-nixos",
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1729697500,
+        "narHash": "sha256-VFTWrbzDlZyFHHb1AlKRiD/qqCJIripXKiCSFS8fAOY=",
+        "owner": "zhaofengli",
+        "repo": "nix-github-actions",
+        "rev": "e418aeb728b6aa5ca8c5c71974e7159c2df1d8cf",
+        "type": "github"
+      },
+      "original": {
+        "owner": "zhaofengli",
+        "ref": "matrix-name",
+        "repo": "nix-github-actions",
+        "type": "github"
+      }
+    },
     "nixos-hardware": {
       "locked": {
         "lastModified": 1762847253,
@@ -371,6 +414,7 @@
         "emacs-overlay": "emacs-overlay",
         "home-manager": "home-manager",
         "impermanence": "impermanence",
+        "jovian-nixos": "jovian-nixos",
         "lanzaboote": "lanzaboote",
         "niri": "niri",
         "nix-doom-emacs-unstraightened": "nix-doom-emacs-unstraightened",