CI fix + add meshcore source as submodules

CI: switch from python:3.12-slim container to ubuntu-latest +
actions/setup-python. The slim image has no node, but
actions/checkout@v4 is a JavaScript action and the runner expects
node inside the job container. Default ubuntu-latest images on
Forgejo (catthehacker/ubuntu:act-*) ship node; setup-python adds
Python on top.

Submodules: vendor MeshCore firmware and meshcore_py source under
reference/ so the firmware/library behavior is verifiable inline
(parse_status field offsets, send_chan_msg's OK-only ack, etc).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.forgejo/workflows/test.yml

@@ -7,12 +7,14 @@ on:
 
 jobs:
   pytest:
-    runs-on: docker
+    runs-on: ubuntu-latest
-    container:
-      image: python:3.12-slim
     steps:
       - uses: actions/checkout@v4
 
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
+
       - name: Install package + test deps
         run: pip install --no-cache-dir -e '.[test]'
 

.gitmodules

@@ -0,0 +1,6 @@
+[submodule "reference/meshcore-firmware"]
+	path = reference/meshcore-firmware
+	url = https://github.com/meshcore-dev/MeshCore.git
+[submodule "reference/meshcore-py"]
+	path = reference/meshcore-py
+	url = https://github.com/meshcore-dev/meshcore_py.git

reference/meshcore-firmware

@@ -0,0 +1 @@
+Subproject commit 1a7b3614a8439894714a58af55ab7f501e6bb928

reference/meshcore-py

@@ -0,0 +1 @@
+Subproject commit 4d0be8788a5c7e80555ff2570e83b2c03985f91d