ci: drop actions/upload-artifact, tolerate existing releases

upload-artifact@v4 talks to GitHub's artifact service and times out on
Gitea. Distribution happens via release assets anyway. Also reuse an
existing release for a tag instead of failing on a 409.

.gitea/workflows/release.yml

@@ -39,11 +39,6 @@ jobs:
           for f in tea-*; do
             sha256sum "$f" > "$f.sha256"
           done
-      - uses: actions/upload-artifact@v4
-        with:
-          name: tea-binaries
-          path: dist/*
-          if-no-files-found: error
       - name: create release + upload assets
         env:
           GITEA_TOKEN: ${{ secrets.GITEA_TOKEN }}
@@ -51,12 +46,17 @@ jobs:
           set -e
           TAG="${GITHUB_REF_NAME}"
           API="${GITHUB_SERVER_URL}/api/v1/repos/${GITHUB_REPOSITORY}"
+          RELEASE_ID="$(curl -sf -H "Authorization: token ${GITEA_TOKEN}" \
+            "${API}/releases/tags/${TAG}" \
+            | python3 -c 'import sys,json;print(json.load(sys.stdin)["id"])' || true)"
+          if [ -z "$RELEASE_ID" ]; then
             RESPONSE="$(curl -sf -X POST \
               -H "Authorization: token ${GITEA_TOKEN}" \
               -H "Content-Type: application/json" \
               "${API}/releases" \
               -d "{\"tag_name\":\"${TAG}\",\"name\":\"${TAG}\"}")"
             RELEASE_ID="$(printf '%s' "$RESPONSE" | python3 -c 'import sys,json;print(json.load(sys.stdin)["id"])')"
+          fi
           for f in dist/tea-*; do
             curl -sf -X POST \
               -H "Authorization: token ${GITEA_TOKEN}" \