Consolidate CI on codex-maintenance.sh; clean up dead scripts and docs

Both check-nixos.yml workflows (GitHub + Gitea) now call
scripts/codex-maintenance.sh instead of a hand-rolled eval-only loop,
closing a real gap: CI previously enforced none of the secret grep,
nixpkgs-fmt, or statix checks that codex-maintenance.sh already runs
locally — nothing was stopping that from regressing. One script now
backs both, instead of two copies that can drift from each other.

codex-maintenance.sh itself is extended to cover buildable surface
that wasn't validated anywhere before: packages.x86_64-linux.*, plus
config.system.build.tarball (lxc-* hosts) and
config.system.build.diskoImagesScript (proxmox-*, excluding the
installer's own proxmox-lxc target, which has no disko config).

Also:
- scripts/prepare-host-key.sh: dropped the redundant
  [path-to-nixos-repo] parameter — it always defaults to the repo the
  script itself lives in now, so a second argument never made sense
  after the nix-auto-installer migration.
- Removed prepare.sh (dead pre-disko manual parted/mkfs/mkswap
  partitioning, fully superseded) and
  scripts/create-linode-installer-disk.sh (incomplete draft for an
  abandoned dd-via-rescue-mode approach; Linode hosts already deploy
  fine through the normal auto-installer flow).
- docs/pxe-boot.md: fixed a stale `nixosConfigurations.pxe-boot` eval
  command (pre-refactor flat name, not a real flake attribute
  anymore) and added a cross-reference to docs/auto-installer.md.
- CLAUDE.md/README.md: full documentation pass reconciling this
  session's changes — modules/installer/, modules/pxe-boot/, the
  LXC/Proxmox image-building deployment paths, corrected the
  password-hash/SSH-key locations in the safety-rules section (both
  had drifted to reference files/paths that no longer exist), and
  added session-workflow guidance to prefer targeted host evals over
  full-repo sweeps for incremental changes (explicitly scoped to
  interactive sessions, not CI).

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

CLAUDE.md

@@ -17,11 +17,19 @@ machines when deployed.
 - Validation is limited to evaluation, linting, formatting checks, and
   `nix build --dry-run --no-link`.
 - Do not add secrets, tokens, private keys, or new password hashes to the repo.
-- This repo currently contains **committed password hashes** (e.g.
-  `prepare.sh`, `hosts/nixos/configuration.nix`) and SSH public keys (e.g.
-  `modules/nix-cache/server.nix`). The hashes are known tech debt — do not use
-  them as a template for new hosts, and flag any *new* secret-like string you
-  encounter instead of committing it.
+- This repo currently contains **committed password hashes** in
+  `modules/installer/common.nix` (the auto-installer's own root/nixos login —
+  a deliberate, documented choice, see `docs/auto-installer.md`, not
+  accidental tech debt) and **SSH public keys** in `variables.nix`
+  (`vars.adminSshKey`, `vars.remoteBuilderAuthorizedKeys`) plus a couple of
+  per-host `KEY` values for beszel-agent auth (`hosts/server/host.nix`,
+  `hosts/nix-cache/host.nix`). Don't use the installer's hardcoded hash as a
+  template for a *real* host — every other host uses sops-nix
+  (`hashedPasswordFile`, see "Security Notes" in `README.md`). Flag any *new*
+  secret-like string you encounter instead of committing it.
+- `host-keys/` is gitignored — locally-generated *private* SSH host keys for
+  the auto-installer (see `docs/auto-installer.md`). Never commit its
+  contents; if `git status` ever shows it as trackable, something is wrong.
 
 ## Commands
 
@@ -50,6 +58,18 @@ maintenance script pulls them via `nix run github:NixOS/nixpkgs/nixos-25.11#<too
 There is no test suite — "correctness" here means the flake evaluates and
 `nixpkgs-fmt`/`statix` are clean.
 
+**In an interactive agent session**, prefer targeted checks over full-repo
+sweeps: after editing one or two hosts/modules, evaluate just the
+`nixosConfigurations.<host>` you touched (plus any `config.system.build.tarball`
+/`diskoImagesScript`/package output affected) rather than looping over every
+host — `codex-maintenance.sh` evaluates 19 hosts plus every package/tarball/
+image variant now and is slow to run after each small change. Reserve a full
+`codex-maintenance.sh` run for changes that plausibly affect every host
+(`modules/common/*`, `flake.nix`, `variables.nix`) or as a final check before
+committing. This is a session-workflow preference only — it does not apply to
+CI, which should keep running the full script on every push/PR regardless of
+diff size; that's the point of it.
+
 ## Architecture
 
 `flake.nix` is the single entry point. It generates one
@@ -93,7 +113,10 @@ removing a host.
   hardware config, imported directly by the platform module itself
   (`../hardware-configuration/vm/{proxmox,linode}.nix`) — **not** wired in
   from `flake.nix`. `lxc.nix` has no hardware-configuration counterpart since
-  containers share the host kernel.
+  containers share the host kernel; instead it imports nixpkgs' own
+  `virtualisation/proxmox-lxc.nix`, which gives every `lxc-*` host a
+  `config.system.build.tarball` output (`pct restore`-ready, no install step
+  — see `docs/auto-installer.md`).
 - `modules/build-types/*.nix` — what a system is for:
   minimal/server/docker/gui/pxe-boot/nix-cache.
 - `modules/common/configuration.nix` — base NixOS config imported by every
@@ -102,8 +125,19 @@ removing a host.
   the `nixos` user; the `nixos` workstation (`gui` build type) has its own,
   other hosts share `modules/common/home.nix`.
 - `modules/disko/proxmox.nix` — declarative disk layout (GPT: ESP + swap +
-  ext4 root) via disko, used by all Proxmox-VM hosts.
+  ext4 root) via disko, used by all Proxmox-VM hosts (`proxmox-*`, not
+  `lxc-*`). Also carries `imageSize`/`imageName`, letting every `proxmox-*`
+  host be built as a standalone, `qm importdisk`-ready `.raw` image with no
+  install step — see `docs/proxmox-images.md`.
 - `modules/boot/efi.nix` — systemd-boot + EFI vars, paired with the disko module.
+- `modules/installer/` — the auto-installer environment (ISO/netboot/Proxmox
+  LXC): `common.nix` (shared config + the generated `auto-install.sh`),
+  `iso.nix`/`proxmox-lxc.nix` (per-variant), `host-keys.nix` (optionally
+  bakes `host-keys/` into the image under `--impure`). See
+  `docs/auto-installer.md`.
+- `modules/pxe-boot/stage-installer-artifacts.nix` — builds the installer's
+  netboot image and stages it on the `pxe-boot` host so its iPXE menu can
+  chain straight to it. See `docs/pxe-boot.md`.
 - `modules/nix-cache/{client,server,remote-builder-client}.nix` — binary cache
   substituter + SSH remote-builder wiring; see `docs/nix-cache.md` for the
   full design (per-host local stores, no shared `/nix/store`, and how the
@@ -129,6 +163,12 @@ duplicating config.
   handling.
 - `docs/pxe-boot.md` — the `pxe-boot` host's iPXE/TFTP/HTTP boot chain and
   directory layout under `/srv/pxe`.
+- `docs/auto-installer.md` — the installer environment (ISO/netboot/Proxmox
+  LXC), `host-keys/` and the sops-nix pre-seeding problem it solves, and why
+  `lxc-*` hosts are deliberately excluded from its menu.
+- `docs/proxmox-images.md` — building `proxmox-*` hosts as standalone `.raw`
+  disk images (disko's image builder) instead of installing, and deploying
+  the result to Proxmox.
 - `docs/flake-lock-automation.md` — how `flake.lock` updates flow through CI
   (scheduled `nix flake update` PR + host-eval-on-PR workflow) and why hosts
   should track the committed lock file rather than `nixos-rebuild --upgrade-all`.