pxe-setup: handle quoted defaults whose comments contain quotes

The production yaml ships `interface: ""                          # e.g. "eth0"`.
The old extractor did `gsub(/^"|"$/, "")` which only strips outer quotes, so
with an inline comment containing quotes it produced garbage like
`"                          # e.g. "eth0`, tripping the idempotency check.

Replaces the two inline extractors with one `extract_yaml_value` helper
that first tries to match `"[^"]*"` (grabbing only the first quoted
value), falling back to strip-trailing-comment + trim for unquoted
values.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

deploy/pxe-setup.sh

@@ -195,24 +195,39 @@ fi
 # outside the pxe: block is passed through unchanged, so hand-tuned
 # server:/database:/notifiers: blocks survive intact.
 
-existing_iface="$(awk '
+# extract_yaml_value <key> <config-path>: reads `  key: "value"  # comment`
+# from inside the pxe: block and prints the bare `value`. Empty or missing
+# key → empty output. The production yaml ships default values like
+# `interface: ""                          # e.g. "eth0"` — so we must
+# strip the trailing comment BEFORE unquoting, or the comment's inner
+# quotes get picked up.
+extract_yaml_value() {
+    local key="$1" path="$2"
+    awk -v key="${key}" '
         /^pxe:/                              { in_pxe=1; next }
         in_pxe && /^[A-Za-z_][A-Za-z0-9_]*:/ { in_pxe=0 }
-    in_pxe && /^[[:space:]]+interface:/ {
-        sub(/^[[:space:]]+interface:[[:space:]]*/, "")
-        gsub(/^"|"$/, "")
-        print; exit
+        in_pxe {
+            re = "^[[:space:]]+" key ":[[:space:]]*"
+            if ($0 ~ re) {
+                line = $0
+                sub(re, "", line)
+                # Quoted value: extract between the first pair of quotes.
+                if (match(line, /"[^"]*"/)) {
+                    print substr(line, RSTART+1, RLENGTH-2)
+                    exit
                 }
-' "${CONFIG}")"
-existing_range="$(awk '
-    /^pxe:/        { in_pxe=1; next }
-    in_pxe && /^[A-Za-z_][A-Za-z0-9_]*:/ { in_pxe=0 }
-    in_pxe && /^[[:space:]]+dhcp_range:/ {
-        sub(/^[[:space:]]+dhcp_range:[[:space:]]*/, "")
-        gsub(/^"|"$/, "")
-        print; exit
+                # Unquoted value: drop any trailing comment + whitespace.
+                sub(/[[:space:]]*#.*$/, "", line)
+                gsub(/^[[:space:]]+|[[:space:]]+$/, "", line)
+                print line
+                exit
             }
-' "${CONFIG}")"
+        }
+    ' "${path}"
+}
+
+existing_iface="$(extract_yaml_value interface  "${CONFIG}")"
+existing_range="$(extract_yaml_value dhcp_range "${CONFIG}")"
 
 if [[ -n "${existing_iface}" && "${existing_iface}" != "${INTERFACE}" && ${FORCE} -eq 0 ]]; then
     echo "ERROR: pxe.interface in ${CONFIG} is already set to ${existing_iface}, which" >&2