docs: clarify Maven staging behavior across release candidates (#3963)

Author: andygrove

docs/source/contributor-guide/release_process.md

@@ -302,8 +302,13 @@ Creating Nexus staging repository
 In the Nexus repository UI (https://repository.apache.org/) locate and verify the artifacts in
 staging (https://central.sonatype.org/publish/release/#locate-and-examine-your-staging-repository).
 
-If the artifacts appear to be correct, then close and release the repository so it is made visible (this should
-actually happen automatically when running the script).
+The script closes the staging repository but does not release it. Releasing to Maven Central is a manual step
+performed only after the vote passes (see [Publishing Maven Artifacts](#publishing-maven-artifacts) below).
+
+Note that the Maven artifacts are always published under the final release version (e.g. `0.13.0`), not the RC
+version — the `-rc1` / `-rc2` suffix only appears in the git tag and the source tarball in SVN. Because the script
+creates a new staging repository on each run, re-staging the same version for a subsequent RC is supported as long
+as no staging repository for that version has been released to Maven Central.
 
 ### Create the Release Candidate Tarball
 
@@ -345,6 +350,13 @@ If the vote does not pass, address the issues raised, increment the release cand
 the [Tag the Release Candidate](#tag-the-release-candidate) step. For example, the next attempt would be tagged
 `0.13.0-rc2`.
 
+Before staging the next RC, drop the previous RC's staging repository in the
+[Nexus UI](https://repository.apache.org/#stagingRepositories) by selecting it and clicking "Drop". This avoids
+leaving multiple closed staging repositories for the same version and prevents accidentally releasing the wrong
+one when the vote eventually passes. The Maven version (e.g. `0.13.0`) is shared across all RCs, so each run of
+`publish-to-maven.sh` creates a new staging repository for the same GAV — only one of them should ever be
+released to Maven Central.
+
 ## Publishing Binary Releases
 
 Once the vote passes, we can publish the source and binary releases.