ci: pin gen-index.sh clone to bread-ecosystem's dev branch

The TRACK-aware gen-index.sh only exists on bread-ecosystem's dev branch
so far (not yet merged to main). Without --branch dev, the remote clone
defaulted to main and silently ran the old track-blind script, which is
why dl.breadway.dev/dev/index.json never actually picked up bread's dev
builds despite the workflow reporting success.

.forgejo/workflows/beta-release.yml

@@ -51,5 +51,7 @@ jobs:
             exit 1
           fi
           rm -rf /tmp/bread-ecosystem-ci
-          git clone https://git.breadway.dev/Breadway/bread-ecosystem.git /tmp/bread-ecosystem-ci
+          # --branch dev: see dev-release.yml — the TRACK-aware gen-index.sh
+          # isn't merged to bread-ecosystem's main yet.
+          git clone --branch dev https://git.breadway.dev/Breadway/bread-ecosystem.git /tmp/bread-ecosystem-ci
           TRACK=beta bash /tmp/bread-ecosystem-ci/scripts/gen-index.sh

.forgejo/workflows/dev-release.yml

@@ -65,5 +65,9 @@ jobs:
             exit 1
           fi
           rm -rf /tmp/bread-ecosystem-ci
-          git clone https://git.breadway.dev/Breadway/bread-ecosystem.git /tmp/bread-ecosystem-ci
+          # --branch dev: the TRACK-aware gen-index.sh isn't merged to
+          # bread-ecosystem's main yet, so a default clone would silently
+          # run the old track-blind script against the stable index instead
+          # of writing dl.breadway.dev/dev/index.json at all.
+          git clone --branch dev https://git.breadway.dev/Breadway/bread-ecosystem.git /tmp/bread-ecosystem-ci
           TRACK=dev bash /tmp/bread-ecosystem-ci/scripts/gen-index.sh