base: install mikefarah yq (pinned v4.53.3), drop Debian python yq

Debian/Ubuntu `apt install yq` is kislyuk/yq (Python, v3.x), incompatible
with the mikefarah v4 syntax the cloud-init repo's provision.sh/deploy.sh
require. Replace the apt package with a pinned mikefarah Go binary, mirroring
the existing tealdeer ARG (latest-or-pin) pattern, multi-arch amd64/arm64.
smoke-test.sh now asserts `yq --version` reports mikefarah so CI catches a
regression. CHANGELOG: Unreleased entry.

Dockerfile.base

@@ -51,7 +51,8 @@ ENV DEBIAN_FRONTEND=noninteractive
 #                  See the bundled `dot-watch` helper for live .dot -> PNG
 #                  re-render (handy with pi-studio's image preview).
 #   imagemagick  — image conversion / resizing for thumbnails, etc. ~50 MB.
-#   yq           — YAML-aware companion to jq.
+#   (yq is NOT apt-installed: Debian's `yq` is the unrelated Python tool;
+#    mikefarah's Go yq is installed as a pinned binary further down.)
 #   socat        — TCP relay. Powers `studio-expose`, which bridges
 #                  pi-studio's container-loopback server to the container's
 #                  external interface so a published port can reach it.
@@ -66,7 +67,6 @@ RUN apt-get update && \
     openssh-client \
     gnupg \
     jq \
-    yq \
     ripgrep \
     fd-find \
     tree \
@@ -404,6 +404,24 @@ RUN ARCH=$(case "${TARGETARCH}" in amd64) echo "x86_64" ;; arm64) echo "aarch64"
     chmod +x /usr/local/bin/tldr && \
     tldr --version
 
+# ── yq (mikefarah) — YAML processor, jq's companion for YAML ─────────
+# Installed as the mikefarah Go binary — NOT Debian's `yq` apt package, which
+# is the unrelated Python kislyuk/yq (a jq wrapper with different syntax and
+# version line, e.g. 3.x). The cloud-init repo's deploy.sh/provision.sh
+# require mikefarah yq v4; pinned here to the v4.x release used on the
+# control machines (override with --build-arg YQ_VERSION=latest|vX.Y.Z).
+ARG YQ_VERSION=v4.53.3
+RUN ARCH=$(case "${TARGETARCH}" in amd64) echo "amd64" ;; arm64) echo "arm64" ;; *) echo "amd64" ;; esac) && \
+    V="${YQ_VERSION}" && \
+    if [ "$V" = "latest" ]; then \
+      V=$(curl -sI --retry 5 --retry-delay 5 --retry-all-errors "https://github.com/mikefarah/yq/releases/latest" | awk 'tolower($1)=="location:" { sub(/\r$/,"",$2); n=split($2,a,"/"); print a[n] }'); \
+    fi && \
+    [ -n "$V" ] && \
+    echo "Installing mikefarah yq ${V}" && \
+    curl -fsSL --retry 5 --retry-delay 5 --retry-all-errors "https://github.com/mikefarah/yq/releases/download/${V}/yq_linux_${ARCH}" -o /usr/local/bin/yq && \
+    chmod +x /usr/local/bin/yq && \
+    yq --version
+
 # ── AWS CLI v2 (for SSO/Bedrock authentication) ─────────────────────
 RUN ARCH=$(case "${TARGETARCH}" in \
       amd64) echo "x86_64" ;; \