cleanup common configs + disable CONFIG_VT if kmscon is enabled

AGENTS.md

@@ -21,7 +21,7 @@ flake.nix                  # 3 hosts, 2 channels
 deploy.sh                  # wrapper: current-host rebuild or `muffin` deploy-rs
 hosts/<host>/              # host entrypoints (default.nix, home.nix, disk.nix, …)
 modules/                   # flat namespace; see module naming below
-  common-*.nix             # imported by ALL hosts (nix settings, doas, fish shim)
+  common.nix               # imported by ALL hosts (nix settings, doas, fish shim)
   desktop-*.nix            # imported by mreow/yarn only
   server-*.nix             # imported by muffin only
   <bare>.nix               # scoped by filename (age-secrets, zfs, no-rgb, …)