Make MAPS submodule track latest (branch=master) and add update helper

.gitmodules

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+[submodule "MAPS"]
+	path = MAPS
+	url = https://github.com/drflei/MSM_maps.git
+	branch = master

MAPS_UPDATE.md

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+# MAPS submodule: tracking latest maps
+
+This repository contains a MAPS submodule that points to the MSM_maps repository. The submodule has been configured to track the upstream branch `master` so you can update it to the latest maps with Git or with the provided helper script.
+
+Options to get the latest maps:
+
+- Using Git (recommended for developers / CI):
+
+  From the repository root:
+
+  ```bash
+  git submodule sync --recursive
+  git submodule update --init --remote MAPS
+  # If you want to persist the new submodule commit in the superproject:
+  git add MAPS
+  git commit -m "Update MAPS submodule to latest"
+  ```
+
+- Using the helper script (convenient for users who don't want to run git submodule commands):
+
+  From the repository root:
+
+  ```bash
+  python3 scripts/update_maps.py
+  ```
+
+Notes:
+- The submodule is configured with `branch = master`. If the upstream branch name changes, update `.gitmodules` accordingly.
+- The helper script calls `git clone` / `git pull` and therefore requires `git` to be installed and network access.

scripts/update_maps.py

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+#!/usr/bin/env python3
+"""
+scripts/update_maps.py
+
+Helper to clone or update the MAPS subrepository (MSM_maps).
+Run from the repository root (or via python -m scripts.update_maps) to ensure the MAPS directory is populated/updated.
+"""
+import os
+import subprocess
+import sys
+
+REPO_URL = "https://github.com/drflei/MSM_maps.git"
+
+# MAPS directory relative to repository root: repo_root/MAPS
+here = os.path.dirname(os.path.abspath(__file__))
+REPO_ROOT = os.path.normpath(os.path.join(here, os.pardir))
+MAPS_DIR = os.path.join(REPO_ROOT, "MAPS")
+
+
+def run(cmd, check=True):
+    print('> ' + ' '.join(cmd))
+    return subprocess.run(cmd, check=check)
+
+
+def ensure_maps():
+    maps_path = os.path.abspath(MAPS_DIR)
+    if not os.path.exists(maps_path):
+        print("Cloning MSM_maps into", maps_path)
+        run(["git", "clone", REPO_URL, maps_path])
+        # ensure the tracked branch exists locally
+        try:
+            run(["git", "-C", maps_path, "checkout", "master"])
+        except subprocess.CalledProcessError:
+            # continue if branch not present locally
+            pass
+    else:
+        print("Pulling latest changes into", maps_path)
+        # fetch and pull the configured remote/master
+        run(["git", "-C", maps_path, "fetch", "--all"])
+        run(["git", "-C", maps_path, "pull", "origin", "master"])
+
+
+if __name__ == "__main__":
+    try:
+        ensure_maps()
+    except subprocess.CalledProcessError as e:
+        print("Error updating MAPS:", e, file=sys.stderr)
+        sys.exit(2)