BC-250 console image: custom GNOME recipe with remote admin

Based on 62fixolab/Latest-Bazzite-AMD-BC-250-Patched-Images @ 347fd4d.

Adds on top of the fork:
- recipes/bc250-console-gnome.yml: governor + gnome-remote-desktop +
  openssh-server, sshd enabled, hhd.service masked, no signing module
  (local build + ISO path)
- files/console/usr/bin/bc250-remote-setup: one-time on-box SSH/RDP setup
- files/console/usr/lib/bootc/kargs.d/50-bc250-ttm.toml: ttm memory kargs
- BUILD-CONSOLE.md: build -> ISO -> validation instructions

files/console/ is separate from files/system/ so the 40-CU unlock tooling
stays out of this stable 24-CU image.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scripts/update-40cu-vendors.sh

@@ -0,0 +1,31 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(git rev-parse --show-toplevel)"
+WORKDIR="$(mktemp -d)"
+
+cleanup() {
+  rm -rf "$WORKDIR"
+}
+trap cleanup EXIT
+
+sync_repo() {
+  local repo="$1"
+  local name="$2"
+  local clone_dir="$WORKDIR/$name"
+
+  gh repo clone "$repo" "$clone_dir" -- --depth 1
+
+  rsync -a --delete --exclude='.git' "$clone_dir/" "$ROOT/vendor/$name/"
+  rsync -a --delete --exclude='.git' "$clone_dir/" "$ROOT/files/system/usr/share/bc250-40cu/vendor/$name/"
+
+  git -C "$clone_dir" rev-parse HEAD > "$ROOT/vendor/$name.UPSTREAM_REF"
+  git -C "$clone_dir" rev-parse HEAD > "$ROOT/files/system/usr/share/bc250-40cu/vendor/$name.UPSTREAM_REF"
+}
+
+mkdir -p "$ROOT/vendor" "$ROOT/files/system/usr/share/bc250-40cu/vendor"
+
+sync_repo duggasco/bc250-40cu-unlock bc250-40cu-unlock
+sync_repo WinnieLV/bc250-cu-live-manager bc250-cu-live-manager
+
+echo "Updated 40CU vendor sources."