feat(xdc-zero): Chain 138 bridge runbook, config fragments, merge helper

- Add CHAIN138_XDC_ZERO_BRIDGE_RUNBOOK and 07-ccip pointer doc
- Add config/xdc-zero templates, parent register fragment, README
- Add merge-endpointconfig-chain138.sh (jq merge, XDC_ZERO_ENDPOINT_DIR)
- Add xdc-zero-chain138-preflight.sh; trim XDC URL vars in load-project-env
- Wire AGENTS.md, MASTER_INDEX, verify README, .env.master.example

Made-with: Cursor

scripts/xdc-zero/merge-endpointconfig-chain138.sh

@@ -0,0 +1,80 @@
+#!/usr/bin/env bash
+# Merge Chain 138 XDC-Zero fragments into an existing endpointconfig.json (upstream XDC-Zero layout).
+# Requires jq. Backs up the target file unless --dry-run or explicit stdout.
+#
+# Usage:
+#   bash scripts/xdc-zero/merge-endpointconfig-chain138.sh path/to/endpointconfig.json
+#   bash scripts/xdc-zero/merge-endpointconfig-chain138.sh path/to/endpointconfig.json path/to/out.json
+#   bash scripts/xdc-zero/merge-endpointconfig-chain138.sh path/to/endpointconfig.json --dry-run
+#   bash scripts/xdc-zero/merge-endpointconfig-chain138.sh --dry-run path/to/endpointconfig.json
+# Or set XDC_ZERO_ENDPOINT_DIR to an XDC-Zero/endpoint clone path (uses .../endpointconfig.json).
+#
+# Sources: config/xdc-zero/endpointconfig.fragment.chain138.example.json,
+#          config/xdc-zero/xdcparentnet-register-chain138.fragment.json
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_ROOT="$(cd "$SCRIPT_DIR/../.." && pwd)"
+FRAG="$PROJECT_ROOT/config/xdc-zero/endpointconfig.fragment.chain138.example.json"
+REG_FRAG="$PROJECT_ROOT/config/xdc-zero/xdcparentnet-register-chain138.fragment.json"
+
+DRY_RUN=false
+BASE=""
+OUT=""
+POSITIONAL=()
+for a in "$@"; do
+  if [[ "$a" == "--dry-run" ]]; then
+    DRY_RUN=true
+  else
+    POSITIONAL+=("$a")
+  fi
+done
+
+if [[ ${#POSITIONAL[@]} -ge 1 ]]; then
+  BASE="${POSITIONAL[0]}"
+fi
+if [[ ${#POSITIONAL[@]} -ge 2 ]]; then
+  OUT="${POSITIONAL[1]}"
+fi
+
+if [[ -z "$BASE" && -n "${XDC_ZERO_ENDPOINT_DIR:-}" ]]; then
+  BASE="${XDC_ZERO_ENDPOINT_DIR%/}/endpointconfig.json"
+fi
+
+if [[ -z "$BASE" || ! -f "$BASE" ]]; then
+  echo "Usage: $0 <endpointconfig.json> [out.json] [--dry-run]" >&2
+  echo "  Or: XDC_ZERO_ENDPOINT_DIR=/path/to/XDC-Zero/endpoint $0 [--dry-run]" >&2
+  exit 1
+fi
+if [[ ! -f "$FRAG" || ! -f "$REG_FRAG" ]]; then
+  echo "ERROR: missing fragment under config/xdc-zero/" >&2
+  exit 1
+fi
+command -v jq >/dev/null 2>&1 || { echo "ERROR: jq required" >&2; exit 1; }
+
+_step1="$(jq --slurpfile f "$FRAG" '.chain138 = $f[0].chain138' "$BASE")"
+MERGED="$(printf '%s\n' "$_step1" | jq --slurpfile r "$REG_FRAG" '
+  (if .xdcparentnet == null then . + {xdcparentnet: {registers: []}} else . end)
+  | .xdcparentnet.registers += $r[0]
+')"
+
+_c138_count="$(printf '%s' "$MERGED" | jq '[.xdcparentnet.registers[]? | select(.chainId == 138)] | length')"
+if [[ "${_c138_count:-0}" -gt 1 ]]; then
+  echo "WARN: xdcparentnet.registers has ${_c138_count} entries with chainId 138 — review manually." >&2
+fi
+
+if $DRY_RUN; then
+  printf '%s\n' "$MERGED"
+  exit 0
+fi
+
+if [[ -n "$OUT" ]]; then
+  printf '%s\n' "$MERGED" >"$OUT"
+  echo "Wrote $OUT"
+  exit 0
+fi
+
+cp -a "$BASE" "${BASE}.bak.$(date +%Y%m%d%H%M%S)"
+printf '%s\n' "$MERGED" >"$BASE"
+echo "Merged into $BASE (backup beside file)."