fix(console): make a failed Steam session diagnosable, add shortcut tooling

Autologin into the gamescope Steam session does not take on the real
hardware; the television lands on ReGreet instead. The config side is
correct -- initial_session is present in the generated greetd.toml and
services.greetd.restart evaluates to false -- so the likely cause is the
session starting and then dying, which greetd answers by falling through
to default_session.

greetd hands a session the VT for its standard streams, so whatever the
session prints on its way down is erased as soon as the greeter repaints.
Run the launcher under systemd-cat so the reason survives in the journal
under the steam-session identifier.

Steam's non-Steam-game Browse dialog and its library-folder picker both
go through the XDG portal FileChooser interface and do not open here
(ValveSoftware/steam-for-linux#9447, #10415). Add steamtinkerlaunch,
which writes shortcuts.vdf without the dialog, and document
library_folder_add as the equivalent route for the library folder.

Docs also catch up with the host's actual state: hardware-configuration
.nix is a real scan now, standalone pcsx2 is installed, and the untested
claims become the list of open problems.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

hosts/Console/gaming.nix

@@ -61,6 +61,14 @@ let
     "clonehero/backgrounds"
   ];
 
+  # greetd gives a session the VT for stdio, so a failed Steam session leaves no
+  # evidence once the greeter takes the VT back. Log to the journal instead:
+  # `journalctl -b -t steam-session`.
+  steamSession = pkgs.writeShellScript "steam-session" ''
+    exec ${pkgs.systemd}/bin/systemd-cat --identifier=steam-session \
+      /run/current-system/sw/bin/steam-gamescope
+  '';
+
   # RetroArch and the cores this machine is expected to run. The wrapper already
   # points RetroArch at the packaged assets, core info and joypad autoconfig
   # profiles; `settings` here is merged on top of those.
@@ -178,13 +186,11 @@ in
   # ask for it; Steam's Proton builds and most native titles do.
   programs.gamemode.enable = true;
 
-  # Autologin into the Steam session. The launcher is not exposed as a package
-  # by the steam module -- it is built inside it and added to
-  # environment.systemPackages -- so reference it through the system profile.
-  # greetd's `restart` option defaults to false once initial_session is set,
-  # which is what stops a logout from looping straight back into autologin.
+  # Autologin into the Steam session. greetd's `restart` option defaults to
+  # false once initial_session is set, which is what stops a logout from looping
+  # straight back into autologin.
   services.greetd.settings.initial_session = {
-    command = "/run/current-system/sw/bin/steam-gamescope";
+    command = "${steamSession}";
     user = tvUser;
   };
 
@@ -242,6 +248,10 @@ in
     pkgs.clonehero
     pkgs.pcsx2
     pkgs.dualsensectl # DualSense LED/battery/mic control from the shell
+    # Writes shortcuts.vdf from the shell. Steam's own "Add a Non-Steam Game"
+    # dialog depends on a working portal file picker and frequently does not
+    # open; see docs/hosts/console.md.
+    pkgs.steamtinkerlaunch
     pkgs.mangohud # FPS/frametime overlay; use `mangohud %command%` in Steam
     pkgs.vulkan-tools # vulkaninfo, for checking the 32/64-bit ICDs Proton needs
   ];