fix(create-proxmox-resource): use absolute path for --pre-format-files

The disko images script does `cd "$TMPDIR"` before parsing its arguments,
so relative paths passed to --pre-format-files resolve against the temp
dir instead of the repo root. Use $(pwd) to capture the absolute repo
path before the disko script changes directory.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/proxmox/create-proxmox-resource.sh

@@ -751,8 +751,8 @@ nix build --no-use-registries --no-accept-flake-config "${NIX_OPTS[@]}" \
   ".#nixosConfigurations.${target}.config.system.build.diskoImagesScript" \
   --out-link "result-${target}"
 $sudo_pfx "./result-${target}" \
-  --pre-format-files "host-keys/${target}_ssh_host_ed25519_key" /etc/ssh/ssh_host_ed25519_key \
-  --pre-format-files "host-keys/${target}_ssh_host_ed25519_key.pub" /etc/ssh/ssh_host_ed25519_key.pub \
+  --pre-format-files "$(pwd)/host-keys/${target}_ssh_host_ed25519_key" /etc/ssh/ssh_host_ed25519_key \
+  --pre-format-files "$(pwd)/host-keys/${target}_ssh_host_ed25519_key.pub" /etc/ssh/ssh_host_ed25519_key.pub \
   --build-memory 2048
 built="$(find . -maxdepth 1 -name '*.raw' -newer "result-${target}" | head -1)"
 if [[ -z "$built" ]]; then