publish iso as nightly github release so it shows on repo front page

Author: MochiOS Team

.github/workflows/build-iso.yml

@@ -5,6 +5,9 @@ on:
     branches: [main]
   workflow_dispatch:
 
+env:
+  RELEASE_TAG: nightly
+
 jobs:
   build:
     runs-on: ubuntu-latest
@@ -59,3 +62,23 @@ jobs:
           name: mochios-iso
           path: /tmp/mochios/out/*.iso
           retention-days: 30
+
+  release:
+    needs: build
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - uses: actions/download-artifact@v4
+        with:
+          name: mochios-iso
+          path: /tmp/iso
+
+      - name: publish release
+        run: |
+          cd /tmp/iso
+          iso=$(ls *.iso 2>/dev/null | head -1)
+          if [ -z "$iso" ]; then echo "no iso found"; exit 1; fi
+          gh release view "$RELEASE_TAG" --json url &>/dev/null && \
+            gh release upload "$RELEASE_TAG" "$iso" --clobber || \
+            gh release create "$RELEASE_TAG" "$iso" --title "MochiOS Nightly" --notes "auto-built from main" --prerelease