[rp2040] Add CI check for boards.py freshness

Add generate-rp2040-boards.py script that clones the arduino-pico
repository at the recommended framework version and regenerates
boards.py, matching the existing ESP32 board generation CI check
pattern.

This ensures boards.py stays in sync when the arduino-pico
framework version is updated.

Follow-up to #14528.

script/generate-rp2040-boards.py

@@ -0,0 +1,61 @@
+#!/usr/bin/env python3
+
+from __future__ import annotations
+
+import argparse
+from pathlib import Path
+import subprocess
+import sys
+import tempfile
+
+from esphome.components.rp2040 import RECOMMENDED_ARDUINO_FRAMEWORK_VERSION
+from esphome.components.rp2040.generate_boards import generate
+from esphome.helpers import write_file_if_changed
+
+ver = RECOMMENDED_ARDUINO_FRAMEWORK_VERSION
+version_tag: str = f"{ver.major}.{ver.minor}.{ver.patch}"
+root: Path = Path(__file__).parent.parent
+boards_file_path: Path = root / "esphome" / "components" / "rp2040" / "boards.py"
+
+
+def main(check: bool) -> None:
+    with tempfile.TemporaryDirectory() as tempdir:
+        subprocess.run(
+            [
+                "git",
+                "clone",
+                "-q",
+                "-c",
+                "advice.detachedHead=false",
+                "--depth",
+                "1",
+                "--branch",
+                version_tag,
+                "https://github.com/earlephilhower/arduino-pico",
+                tempdir,
+            ],
+            check=True,
+        )
+
+        content: str = generate(Path(tempdir))
+
+    if check:
+        existing_content: str = boards_file_path.read_text(encoding="utf-8")
+        if existing_content != content:
+            print("esphome/components/rp2040/boards.py is not up to date.")
+            print("Please run `script/generate-rp2040-boards.py`")
+            sys.exit(1)
+        print("esphome/components/rp2040/boards.py is up to date")
+    elif write_file_if_changed(boards_file_path, content):
+        print("RP2040 boards updated successfully.")
+
+
+if __name__ == "__main__":
+    parser: argparse.ArgumentParser = argparse.ArgumentParser()
+    parser.add_argument(
+        "--check",
+        help="Check if the boards.py file is up to date.",
+        action="store_true",
+    )
+    args: argparse.Namespace = parser.parse_args()
+    main(args.check)