Remove packages.all bundle and the installer's own proxmox-lxc target

Both existed only so the installer could boot as an LXC container and
nixos-install some other host from within it, but lxc-* targets are
already excluded from the install menu (nixos-install can't touch its
own running root filesystem), and now have their own direct tarball
path anyway. That left the installer's own LXC form with no real use
case, and packages.all with only two members worth bundling.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01La55Nsss8jZ7ZuzUV9mfot

docs/auto-installer.md

@@ -5,8 +5,9 @@ install any host exposed by its own `nixosConfigurations`. It was migrated
 from a formerly-separate `nix-auto-installer` repo — everything it did now
 lives here.
 
-The installer provides a small NixOS install environment (ISO/netboot/Proxmox
-LXC) with SSH access, Git support, and an interactive installation script.
+The installer provides a small NixOS install environment (ISO, or the same
+image netbooted via PXE) with SSH access, Git support, and an interactive
+installation script.
 Logging in as any user (root or `nixos`) runs `/etc/auto-install.sh`,
 discovers available hosts from this same flake, lets the operator choose a
 target, applies that host's Disko storage configuration, installs NixOS, and
@@ -53,8 +54,6 @@ it does for the ISO/PXE installer images.
   `installation-cd-minimal.nix` module plus `common.nix`. Also used, paired
   with `netboot-minimal.nix`, to build the PXE netboot variant (see
   `docs/pxe-boot.md`).
-- `modules/installer/proxmox-lxc.nix` — Proxmox LXC-specific: disables
-  bootloader options (containers don't need one) plus `common.nix`.
 - `modules/installer/host-keys.nix` — optionally bakes pre-generated SSH
   host keys into the image; see "Host keys" below.
 - `scripts/prepare-host-key.sh` — admin-workstation pre-flight tool, see
@@ -63,22 +62,26 @@ it does for the ISO/PXE installer images.
 Flake outputs:
 
 ```nix
-nixosConfigurations.installer     # ISO/netboot installer image
-nixosConfigurations.proxmox-lxc   # Proxmox LXC-based installer image
+nixosConfigurations.installer   # ISO/netboot installer image
 
 packages.x86_64-linux.iso   # installer ISO/netboot image
-packages.x86_64-linux.lxc   # Proxmox LXC installer tarball
 packages.x86_64-linux.pxe   # netboot-ipxe + netboot-initrd + netboot-kernel, bundled
-packages.x86_64-linux.all   # all three of the above, bundled
 ```
 
 ```sh
 nix build .#iso
-nix build .#lxc
 nix build .#pxe
-nix build .#all
 ```
 
+There's no `nixosConfigurations.proxmox-lxc` (installer-boots-as-an-LXC-
+container) or `packages.x86_64-linux.lxc`/`.all` anymore. Both existed only
+to let the installer itself run as an LXC container so you could
+`nixos-install` some *other* host from within it — but LXC targets are
+excluded from the install menu (same bind-mount problem as any LXC
+`nixos-install`), and now have their own direct tarball path anyway (see
+"LXC hosts" above), which left the installer's own LXC form with no real
+use case.
+
 The `pxe` variant is also built automatically as part of the `pxe-boot` host
 itself (`modules/pxe-boot/stage-installer-artifacts.nix`) and served over
 iPXE — see `docs/pxe-boot.md`.