vmix CLI, laptop images, SDL display

CLI (nix run .#):
- `vmix build` and `vmix copy` subcommands
- --image, --generalize key=val, --to-disk, --to-remote-disk
- SDL display auto-detected via DISPLAY temp file passthrough
- --print-build-logs for visible build progress
- -S 4k sparse writes for faster disk copy

Images:
- win10.laptop and win11.laptop bundles (no VirtIO, keeps defender/hibernation)
- templates.bundles.laptop shared template list
- win11 adds reg.disableUCPD on top

Build improvements:
- consistent === vmix: === log prefixes
- SDL display via /tmp/.vmix-display-$$ temp file

Env helpers:
- .env-export-vmix-cli-local: vmix alias for local flake

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

flake.lock

@@ -2,16 +2,16 @@
   "nodes": {
     "nixpkgs": {
       "locked": {
-        "lastModified": 1715534503,
-        "narHash": "sha256-5ZSVkFadZbFP1THataCaSf0JH2cAH3S29hU9rrxTEqk=",
-        "owner": "nixos",
+        "lastModified": 1779102034,
+        "narHash": "sha256-vZJZjLo513IeI8hjzHFc6TDezUd4uCE2Eq4SNO3DNNg=",
+        "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "2057814051972fa1453ddfb0d98badbea9b83c06",
+        "rev": "687f05a9184cad4eaf905c48b63649e3a86f5433",
         "type": "github"
       },
       "original": {
-        "owner": "nixos",
-        "ref": "nixos-unstable",
+        "owner": "NixOS",
+        "ref": "nixos-25.11",
         "repo": "nixpkgs",
         "type": "github"
       }