docs(#3216): add E2E retry pattern guidance to AGENTS.md

[fullsend-ai-coder]

Add a "Retry Pattern" subsection to the E2E Testing section (after "Best Practices") documenting the preference for Playwright's native expect().toPass() over manual for-loop retry constructs with try/catch.

This addresses a gap where agents suggested manual retry loops instead of the established codebase convention. The pattern is already used in 8 places across topology, bulk-import, and global-header workspaces.

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Closes #3216

Post-script verification

• Branch is not main/master (agent/3216-add-retry-pattern-guidance)
• Secret scan passed (gitleaks — 03870936696ab9cab38483503fc5bad317b69bc8..HEAD)
• Pre-commit hooks passed (authoritative run on runner)
• Tests ran inside sandbox

[openshift-ci]

Hi @fullsend-ai-coder[bot]. Thanks for your PR.

I'm waiting for a redhat-developer member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work.

Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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