fix(devcontainer): bake wg + qrencode into the image instead of splitting the VPN procedure across host and container

Operator correction: "sop, wg, and any other tool requirement is supposed to be
baked into the devcontainer."

My previous commit discovered that `wg` existed only on the host, `sops` only in
the container, and `qrencode` on neither -- and fixed it the wrong way, by
splitting every step of the key procedure across the boundary and telling the
operator to `dnf install qrencode` on their workstation. That breaks CLAUDE.md §5
and the devcontainer README's "Don't install the toolchain on the host", produces
a procedure that cannot be reproduced in CI, and is miserable to follow.

wireguard-tools + qrencode are now distro packages in the Containerfile. Both are
in Fedora 44's repos (wireguard-tools 1.0.20260223 -- the same upstream version as
the image this component runs -- and qrencode 4.1.1), unpinned like every other
dnf package there: the pinned thing is the Fedora base, and neither is a gate tool
whose version changes what green means.

Three things got SIMPLER rather than merely relocated, which is the tell that the
rule was right:

  * Step 2 is one pipeline in one shell -- `sops set ... "$(wg genkey)"` writes the
    key straight into the already-encrypted document. No staged copy in .cache, no
    `*.key`-suffix warning, no sha256 comparison to prove the right bytes landed.
  * new-peer.sh derives the server public key from wg-server-key.sops.yaml itself
    (`sops -d --extract | wg pubkey`), so there is no local key copy to keep in
    step with the encrypted one, and no magic host path it must live at.
  * `.cache/` is gitignored at the repo root (mirroring infra/ansible/.gitignore),
    giving the container a persistent non-committable scratch dir. new-peer.sh
    writes profiles to .cache/wg-peers/ -- necessary because the repo bind-mount is
    the container's only persistent read-write mount, so a profile in /tmp there is
    gone before it can reach a desktop. Its blanket "refuse to write inside the
    checkout" guard is now a `git check-ignore` test of the real property.

Verified by execution, not reasoning: the image rebuilds; wg/qrencode/sops all
resolve in it; `sops -d | wg pubkey` runs in one shell; new-peer.sh refuses the
REPLACE-ME placeholder with an actionable message; and a full run with a throwaway
server key renders a correct profile at 0600 under a 0700 gitignored dir, prints
the QR, and refuses a non-ignored destination inside the repo.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

infra/devcontainer/Containerfile

@@ -32,9 +32,23 @@ ARG TARGETARCH=amd64
 # Distro packages: libvirt client libs (harmless disk-image utilities), ansible, ssh,
 # disk-image + cloud-init seed tooling, python3-pip (for the pip-installed test tools),
 # diffutils (provides `diff`, used by L1 golden render checks), and common utilities.
+#
+# wireguard-tools + qrencode serve the REMOTE-ACCESS VPN (platform/vpn-ingress):
+#   * wireguard-tools gives `wg genkey` / `wg pubkey`, needed to mint the server key and to derive
+#     every client profile's `[Peer] PublicKey` (infra/vpn-ingress/new-peer.sh).
+#   * qrencode renders a client profile as a QR code, which is how a PHONE gets enrolled.
+# They are here rather than on the operator's host because this image is THE toolchain
+# (CLAUDE.md §5; README "Don't install the toolchain on the host"). That rule was briefly broken
+# by a runbook that told the operator to run `wg` on the host and `sops` in here, and then split
+# every step across the boundary to work around it — a procedure nobody should have to follow, and
+# one that cannot be reproduced in CI. Both tools in one image means `sops -d … | wg pubkey` is
+# just a pipeline again.
+# Unpinned on purpose, like every other dnf package here: the Fedora base is what is pinned
+# (FEDORA_VERSION), and these are not gate tools whose version changes what green means.
 RUN dnf -y install --setopt=install_weak_deps=False \
       libvirt-client qemu-img cloud-utils genisoimage openssh-clients \
       ansible-core python3-libvirt python3-pip diffutils \
+      wireguard-tools qrencode \
       git make jq unzip tar gzip xz which ca-certificates curl \
  && dnf clean all