fix(release): add non-blocking Maven Central propagation verify (#175)

Previously the workflow reported "Deploy successful" the moment Sonatype
Central validated the upload (per the v8.0.0 release at 2026-05-09 15:37Z),
then proceeded straight to creating the GitHub Release. But actual public
availability on `repo1.maven.org/maven2` lags by 10-30 minutes for
typical releases — operators were left guessing whether the release was
truly consumable.

Add a polling step between `mvn deploy` and the GitHub Release that
checks `repo1.maven.org` for the artifact .pom directly. Up to 30
minutes (60 × 30s). Non-blocking via `continue-on-error: true` so that:

- Fast propagation: workflow reports Maven Central availability in
  under a minute and the GH release fires.
- Slow propagation (>30min): polling step warns and the GH release
  still fires, leaving the operator with a clear pointer to the
  Sonatype publish dashboard for follow-up.

Verified locally that the new polling logic returns success on first
attempt against both the prior v7.1.0 release and the just-published
v8.0.0 (which has now propagated since the v8.0.0 release ran).

Signed-off-by: Saurabh Jain <saurabhjain1592@gmail.com>

Author: saurabhjain1592

.github/workflows/release.yml

@@ -164,6 +164,33 @@ jobs:
             sleep 60
           done
 
+      - name: Verify version is live on Maven Central
+        # `mvn deploy` reports "Deploy successful" the moment the artifact is
+        # validated by Sonatype Central, but actual public availability on
+        # repo1.maven.org/maven2 lags by 10-30 minutes for typical releases.
+        # We poll up to ~30 minutes (60 × 30s) so the workflow's "completed"
+        # state aligns with public-availability rather than just upload-success.
+        # Non-blocking: a failure here does NOT fail the workflow (the GH release
+        # step still fires) — propagation can occasionally exceed 30 min, in
+        # which case we want the GH release published anyway and the warning
+        # surfaced for operator follow-up.
+        continue-on-error: true
+        run: |
+          VERSION="${{ steps.version.outputs.VERSION }}"
+          POM_URL="https://repo1.maven.org/maven2/com/getaxonflow/axonflow-sdk/${VERSION}/axonflow-sdk-${VERSION}.pom"
+          for i in $(seq 1 60); do
+            if curl -sf -o /dev/null "$POM_URL"; then
+              echo "✅ axonflow-sdk:${VERSION} is live on Maven Central (after ${i} attempt(s) — ~$((i*30))s)"
+              echo "   $POM_URL"
+              exit 0
+            fi
+            echo "Waiting for Maven Central propagation… (attempt ${i}/60)"
+            sleep 30
+          done
+          echo "::warning::axonflow-sdk:${VERSION} not yet on repo1.maven.org after 30 minutes."
+          echo "::warning::Sonatype \`mvn deploy\` succeeded earlier in this job; propagation is sometimes >30 min."
+          echo "::warning::Verify manually at https://central.sonatype.com/publishing/deployments and $POM_URL ; not blocking the GitHub release."
+
       - name: Download release body artifact
         uses: actions/download-artifact@d3f86a106a0bac45b974a628896c90dbdf5c8093 # v4
         with: