fix(dev-fresh): keyless launch no longer crashes on stock macOS bash 3.2 (#144)

Expanding the empty KEY_SETUP_EXTERNAL_KEYS array under set -u is a fatal
'unbound variable' on bash 3.2, which macOS ships as /bin/bash — so a keyless
./scripts/dev-fresh.sh died at the provenance-marker line before doing
anything. The ${arr[*]:-} guard keeps 3.2 alive and leaves populated launches
byte-identical (same idiom the script already uses for DEV_UNSET).

Verified with /bin/bash 3.2.57: the extracted block runs clean under set -u
with no keys (empty CSV) and with keys (ordered comma-joined names); the full
launcher boots keyless to a live server, and exported keys still classify as
externally managed in Provider Settings. A behavioral guard now runs the real
block from the script both ways in the dev-fresh test surface, plus a textual
assertion pinning the 3.2-safe idiom.

scripts/dev-fresh.sh

@@ -38,7 +38,7 @@ KEY_SETUP_EXTERNAL_KEYS=()
 [[ -n "${OPENSKY_CLIENT_ID:-}" ]] && KEY_SETUP_EXTERNAL_KEYS+=(OPENSKY_CLIENT_ID)
 [[ -n "${OPENSKY_CLIENT_SECRET:-}" ]] && KEY_SETUP_EXTERNAL_KEYS+=(OPENSKY_CLIENT_SECRET)
 [[ -n "${LL2_API_TOKEN:-}" ]] && KEY_SETUP_EXTERNAL_KEYS+=(LL2_API_TOKEN)
-KEY_SETUP_EXTERNAL_KEYS_CSV="$(IFS=,; printf '%s' "${KEY_SETUP_EXTERNAL_KEYS[*]}")"
+KEY_SETUP_EXTERNAL_KEYS_CSV="$(IFS=,; printf '%s' "${KEY_SETUP_EXTERNAL_KEYS[*]:-}")"
 
 if command -v npm >/dev/null 2>&1; then
   DEV_COMMAND=(npm run dev --)