NO-JIRA: [RHCOS10] Test existing UBI9 base images on RHCOS10 nodes (no changes)

.work/compliance/rhcos10/PR1-ubi9-compat-test.md

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+# RHCOS10 UBI9 Compatibility Test
+
+## Purpose
+
+Validate that the existing UBI9-based container images used by `ansible-operator-plugins`
+run correctly on RHCOS10 cluster nodes **without any changes**.
+
+RHCOS10 ships with RHEL10 as its host OS. This PR triggers CI against an RHCOS10 cluster
+to confirm UBI9 containers remain compatible before committing to a base image migration.
+
+No Dockerfile changes. This is a baseline/smoke test only.
+
+## Scope
+
+Product images currently use `registry.access.redhat.com/ubi9/ubi-minimal:9.7` as their
+final base image. CI/release images use `registry.ci.openshift.org/ocp/4.22:base-rhel9`
+as their base.
+
+| Image / Dockerfile                            | Current Base Image                                                 |
+| --------------------------------------------- | ------------------------------------------------------------------ |
+| `images/ansible-operator/Dockerfile`          | `registry.access.redhat.com/ubi9/ubi-minimal:9.7` (2 stages)      |
+| `images/ansible-operator/pipfile.Dockerfile`  | `registry.access.redhat.com/ubi9/ubi-minimal:9.7`                 |
+| `openshift/Dockerfile`                        | `registry.ci.openshift.org/ocp/builder:rhel-9-golang-*` (builder) |
+|                                               | `registry.ci.openshift.org/ocp/4.22:base-rhel9` (runtime)         |
+| `openshift/Dockerfile.requirements`           | `registry.ci.openshift.org/ocp/4.22:base-rhel9`                   |
+| `openshift/release/ansible/Dockerfile.collections` | `registry.ci.openshift.org/ocp/4.22:base-rhel9`              |
+
+## Expected Outcome
+
+- All CI jobs pass on RHCOS10 nodes with UBI9 images unchanged.
+- Confirms backward compatibility and green baseline before migration.
+
+## Follow-up
+
+If CI passes → PR2 (`rhcos10-ubi10-migration`) migrates all base images from UBI9/RHEL9 to UBI10/RHEL10.