[CP 1683] docs: clarify v1.5.1 OpenShift catalog version

docs-internal/knowledge/plans/2026-09-23-openshift-v151-operatorhub-note.md

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+# v1.5.1 OpenShift OperatorHub Version Note
+
+- **Date:** 2026-09-23
+- **Author:** Yan Sun
+- **Related PR(s):** TBD
+- **Related issue(s) / JIRA:** N/A
+
+## Context
+
+The v1.5.1 release was intended to use the same version in the OpenShift
+OperatorHub catalog. Because the v1.5.1 OpenShift OLM bundle contained an
+image SHA256 mismatch, a follow-up v1.5.2 bundle was published to the
+certified-operators catalog. As a result, OpenShift users installing the
+v1.5.1 release through OperatorHub see v1.5.2.
+
+Without an explanation, this version difference can appear to be an
+unexpected release or an inconsistency between the general release and the
+OpenShift installation path.
+
+## Approach
+
+Add a version note to the v1.5.1 section of `docs/releasenotes.md` that:
+
+- explicitly scopes the discrepancy to the v1.5.1 release;
+- explains that the follow-up v1.5.2 bundle was required by the image SHA256
+  mismatch; and
+- tells OpenShift users to use v1.5.2 for the v1.5.1 OLM installation.
+
+## Scope
+
+- **In scope:** The v1.5.1 release-notes explanation of the OpenShift
+  OperatorHub version.
+- **Out of scope:** Operator code, OLM manifests, catalog contents, and
+  changes to the general release version.
+
+## Validation
+
+- `git diff --check` passes.
+- Confirm the note appears under the v1.5.1 release-notes heading.
+- Confirm the OpenShift installation guide remains unchanged.
+
+## Risks and rollback
+
+- **Risk:** Readers could interpret v1.5.2 as a separate feature release.
+  The note identifies it as the follow-up OLM bundle for v1.5.1.
+- **Rollback:** Revert the documentation commit; no runtime impact.