bootstrap.sh: require python3 + PyYAML (used by homelab CLI)

The homelab CLI imports yaml; missing on a fresh LXC. Preflight now
checks and emits the right install hint per OS.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

bootstrap.sh

@@ -103,16 +103,28 @@ echo "[bootstrap] hostname: $HNAME"
 
 # Check dependencies.
 missing=()
-for cmd in git; do command -v "$cmd" >/dev/null || missing+=("$cmd"); done
+for cmd in git python3; do command -v "$cmd" >/dev/null || missing+=("$cmd"); done
+# The homelab CLI needs PyYAML.
+if ! python3 -c "import yaml" >/dev/null 2>&1; then
+    missing+=("python3-yaml")
+fi
 if [ "$NO_SECRETS" -eq 0 ]; then
     for cmd in age sops; do command -v "$cmd" >/dev/null || missing+=("$cmd"); done
 fi
 if [ "${#missing[@]}" -gt 0 ]; then
     echo "missing required tools: ${missing[*]}" >&2
     if [ "$OS" = "Darwin" ]; then
-        echo "  brew install ${missing[*]}"
+        # Translate Debian package names to brew/pip equivalents.
+        brew_list=()
+        for m in "${missing[@]}"; do
+            case "$m" in
+                python3-yaml) echo "  pip3 install pyyaml  (or brew install pyyaml)" >&2 ;;
+                *) brew_list+=("$m") ;;
+            esac
+        done
+        [ "${#brew_list[@]}" -gt 0 ] && echo "  brew install ${brew_list[*]}" >&2
     else
-        echo "  apt install -y ${missing[*]}  (or platform equivalent)"
+        echo "  apt install -y ${missing[*]}" >&2
     fi
     exit 1
 fi