[CI] Fill in empty draft releases without touching published ones

The existence check skipped release creation for any existing release, which left a draft saved from the GitHub UI empty and silently reused a published release. Inspect the release instead: create it when missing, fill in the title, notes and prerelease flag of an empty draft, and leave a draft that already has a body or a published release untouched.

.github/workflows/desktop-build.yml

@@ -73,7 +73,7 @@ jobs:
           TAG: ${{ steps.configure.outputs.tag }}
         run: .ci/prep_release.sh
 
-      - name: "Create release"
+      - name: "Create or update draft release"
         if: steps.configure.outputs.tag != null
         id: create_release
         shell: bash
@@ -85,9 +85,15 @@ jobs:
           body_path: ${{ steps.prepare.outputs.body_path }}
           prerelease: ${{ steps.prepare.outputs.is_beta }}
         run: |
-          if gh release view "$tag_name" >/dev/null 2>&1; then
+          # A release for this tag may already exist: a maintainer can save a draft in
-            echo "::warning::Release $tag_name already exists"
+          # the GitHub UI before pushing the tag, or an earlier run may have left one.
-          else
+          # Never touch a published release, and never overwrite a draft that already
+          # has a body (generated notes or a maintainer's edits) - only fill in an
+          # empty draft. Prints "<isDraft> <body length>"; empty when there is none.
+          release_state="$(gh release view "$tag_name" --json isDraft,body \
+            --template '{{.isDraft}} {{len (or .body "")}}' 2>/dev/null || true)"
+
+          if [[ -z "$release_state" ]]; then
             args=()
             [[ $prerelease == yes ]] && args+=(--prerelease)
 
@@ -95,6 +101,18 @@ jobs:
               --target "$target" \
               --title "$release_name" \
               --notes-file "$body_path"
+          elif [[ "$release_state" == "true 0" ]]; then
+            echo "Filling in the empty draft release $tag_name"
+            args=(--prerelease=false)
+            [[ $prerelease == yes ]] && args=(--prerelease)
+
+            gh release edit "$tag_name" "${args[@]}" \
+              --title "$release_name" \
+              --notes-file "$body_path"
+          elif [[ "$release_state" == true* ]]; then
+            echo "::warning::Draft release $tag_name already has a body, leaving it untouched"
+          else
+            echo "::warning::Release $tag_name is already published, leaving it untouched"
           fi
 
   build-linux: