forge: step 2 — add representative build tooling

.github/workflows/firmware-build.yml

@@ -0,0 +1,50 @@
+name: Firmware Build
+
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+  workflow_dispatch:
+
+jobs:
+  representative-build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v4
+        with:
+          submodules: recursive
+
+      - name: Cache PlatformIO
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cache/pip
+            ~/.platformio/.cache
+          key: ${{ runner.os }}-pio
+
+      - name: Install Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.11'
+
+      - name: Install PlatformIO
+        run: python3 -m pip install --upgrade platformio
+
+      - name: Build representative firmware
+        run: bash scripts/build-representative.sh --baseline
+
+      - name: Upload size reports
+        uses: actions/upload-artifact@v4
+        if: always()
+        with:
+          name: representative-size-reports
+          path: out/size
+
+      - name: Upload firmware artifacts
+        uses: actions/upload-artifact@v4
+        if: always()
+        with:
+          name: representative-firmware
+          path: out/firmware