Add completion marker to prevent duplicate discussion posts

- Add mark-release-complete job to release.yml that creates and uploads
  release-complete.json marker to GitHub Release after all release jobs finish
- Add check-release-complete job to release-post-comment.yml that downloads
  and verifies the completion marker before posting to discussions
- Update post-discussion job to depend on check-release-complete instead of
  check-release-exists to ensure only the 4th run (after full completion) posts

This fixes the issue where all 4 workflow_run instances created duplicate
discussion posts because timestamp-based checks were insufficient. The completion
marker ensures only the final run (after release artifacts are complete) posts
to discussions.

Author: oberstet

.github/workflows/release-post-comment.yml

@@ -139,6 +139,76 @@ jobs:
 
           echo '─────────────────────────────────────────────────'
 
+  check-release-complete:
+    name: Check if release is complete (Early Exit Pattern)
+    needs: [identifiers, check-release-exists]
+    # Only check completion for nightly and stable releases
+    if: |
+      needs.check-release-exists.outputs.should_process == 'true' &&
+      (needs.identifiers.outputs.release_type == 'nightly' || needs.identifiers.outputs.release_type == 'stable')
+    runs-on: ubuntu-latest
+    outputs:
+      should_process: ${{ steps.check.outputs.should_process }}
+      is_complete: ${{ steps.check.outputs.is_complete }}
+
+    steps:
+      - name: Check for completion marker in GitHub Release
+        id: check
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          echo '─────────────────────────────────────────────────'
+          echo '🔍 Checking if release is complete (Early Exit Pattern)'
+          echo '─────────────────────────────────────────────────'
+
+          RELEASE_NAME="${{ needs.check-release-exists.outputs.release_name }}"
+          RELEASE_TYPE="${{ needs.identifiers.outputs.release_type }}"
+
+          echo "Release name: $RELEASE_NAME"
+          echo "Release type: $RELEASE_TYPE"
+          echo ""
+
+          # Try to download the completion marker from the GitHub Release
+          echo "Attempting to download release-complete.json marker..."
+
+          if gh release download "$RELEASE_NAME" \
+            --repo "$GITHUB_REPOSITORY" \
+            --pattern "release-complete.json" \
+            --dir . 2>/dev/null; then
+
+            echo "✅ Completion marker found!"
+            echo ""
+            echo "Completion marker contents:"
+            cat release-complete.json
+            echo ""
+
+            # Verify the marker is for the correct release
+            MARKER_RELEASE=$(jq -r '.release_name' release-complete.json)
+            if [ "$MARKER_RELEASE" = "$RELEASE_NAME" ]; then
+              echo "✅ Completion marker matches release name - proceeding"
+              {
+                echo "should_process=true"
+                echo "is_complete=true"
+              } >> $GITHUB_OUTPUT
+            else
+              echo "⚠️  Completion marker mismatch (marker: $MARKER_RELEASE, expected: $RELEASE_NAME)"
+              {
+                echo "should_process=false"
+                echo "is_complete=false"
+              } >> $GITHUB_OUTPUT
+            fi
+          else
+            echo "⏳ Completion marker not found yet"
+            echo "   This is normal! Will post once release.yml completes the release."
+            echo "   (This is an early exit - release.yml is still building artifacts)"
+            {
+              echo "should_process=false"
+              echo "is_complete=false"
+            } >> $GITHUB_OUTPUT
+          fi
+
+          echo '─────────────────────────────────────────────────'
+
   # Development release: Post PR summary comment for development builds
   post-pr-comment:
     name: Post PR Comment (Development Builds)
@@ -278,13 +348,13 @@ jobs:
   # Nightly and Stable releases: Post to GitHub Discussions
   post-discussion:
     name: Post to GitHub Discussions (Nightly & Stable)
-    needs: [identifiers, check-release-exists]
+    needs: [identifiers, check-release-exists, check-release-complete]
     runs-on: ubuntu-latest
 
     # Only run for nightly or stable builds (explicit positive list)
-    # With timestamp verification in check-release-exists, only the 4th run should proceed
+    # With completion marker verification in check-release-complete, only the 4th run should proceed
     if: |
-      needs.check-release-exists.outputs.should_process == 'true' &&
+      needs.check-release-complete.outputs.should_process == 'true' &&
       (needs.identifiers.outputs.release_type == 'nightly' || needs.identifiers.outputs.release_type == 'stable')
 
     env:

.github/workflows/release.yml

@@ -381,3 +381,52 @@ jobs:
           else
             echo "⚠️  RTD_TOKEN not configured, skipping RTD build trigger"
           fi
+
+  # Mark release as complete (for release-post-comment to detect)
+  mark-release-complete:
+    name: Mark Release Complete
+    needs: [identifiers, release-nightly, release-stable]
+    if: always() && needs.identifiers.result == 'success' && (needs.release-nightly.result == 'success' || needs.release-stable.result == 'success')
+    runs-on: ubuntu-latest
+
+    env:
+      RELEASE_TYPE: ${{ needs.identifiers.outputs.release_type }}
+      RELEASE_NAME: ${{ needs.identifiers.outputs.release_name }}
+
+    steps:
+      - name: Create completion marker
+        run: |
+          echo "==> Creating release completion marker..."
+          echo "Release: $RELEASE_NAME"
+          echo "Type: $RELEASE_TYPE"
+
+          # Create completion marker JSON with metadata
+          cat > release-complete.json <<EOF
+          {
+            "release_name": "$RELEASE_NAME",
+            "release_type": "$RELEASE_TYPE",
+            "completed_at": "$(date -u +'%Y-%m-%dT%H:%M:%SZ')",
+            "workflow_run_id": "${{ github.run_id }}",
+            "commit_sha": "${{ needs.identifiers.outputs.head_sha }}",
+            "nightly_status": "${{ needs.release-nightly.result }}",
+            "stable_status": "${{ needs.release-stable.result }}"
+          }
+          EOF
+
+          echo ""
+          echo "Completion marker contents:"
+          cat release-complete.json
+
+      - name: Upload completion marker to GitHub Release
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          echo "==> Uploading completion marker to release $RELEASE_NAME..."
+
+          # Upload the completion marker as a release asset
+          gh release upload "$RELEASE_NAME" \
+            release-complete.json \
+            --repo "$GITHUB_REPOSITORY" \
+            --clobber
+
+          echo "✅ Completion marker uploaded successfully"