Add AGENTS.md guidance to apply E2E config changes to all YAML variants in a workspace

Read the AGENTS.md E2E testing section and inspect workspaces//e2e-tests/tests/config/ alongside workspaces//metadata/*.yaml for the referenced configuration patterns. Add a brief note reminding agents to compare sibling YAML variants and matching metadata entries, then confirm it covers the dynamic-plugins examples and validation criteria in this issue.

What happened

In PR #3047, the code agent (run 30613740954) added module: Legacy to workspaces/bulk-import/e2e-tests/tests/config/dynamic-plugins.yaml but missed the sibling file dynamic-plugins-with-orchestrator.yaml in the same directory, which had the same entries needing the same fix. The review agent caught this (run 31804541146), and a human-directed fix iteration was required to update the sibling file (run 31814351597). The same pattern applied to the metadata YAML, which also needed the change. This added one full fix+review cycle (~2.5 hours elapsed).

What could go better

The code agent modified one config file without checking whether other YAML files in the same directory contained similar sections needing the same change. The e2e-tests/tests/config/ directory can contain multiple dynamic plugin config variants (e.g., dynamic-plugins.yaml and dynamic-plugins-with-orchestrator.yaml) that share the same plugin entries. Any change to plugin configuration in one variant almost certainly needs to be applied to all variants.

The review agent did catch this (demonstrating good value), but the code agent should aim to get this right on the first attempt to reduce rework.

Confidence: Medium-high. The pattern is clear for this workspace, but the prevalence of multi-variant config directories across workspaces is uncertain. Most workspaces may only have a single config file.

Proposed change

Add a brief note to the AGENTS.md E2E testing section (under "Configuration Files" or as a new tip) advising:

When modifying any file in workspaces/<name>/e2e-tests/tests/config/, list all YAML files in that directory and check whether sibling files contain similar sections that require the same change. For example, dynamic-plugins.yaml and dynamic-plugins-with-orchestrator.yaml may share the same plugin entries — a change to one typically requires the same change to all variants. Similarly, check whether workspaces/<name>/metadata/*.yaml contains spec.appConfigExamples sections with the same entries, which should be kept consistent.

This is a lightweight addition (2-3 sentences) that directly addresses the missed-sibling-file pattern.

Validation criteria

In the next 5 code agent PRs that modify files in a workspace's e2e-tests/tests/config/ directory, the code agent should check and update all YAML variants in the same directory that contain matching sections. The review agent should not need to flag missed sibling config files as a finding in any of these PRs.

Generated by retro agent from https://github.com/redhat-developer/rhdh-plugin-export-overlays/pull/3047