:seedling: Collect support-bundle diagnostics on e2e failure (#2750)

* :seedling: Collect support-bundle diagnostics on e2e failure

Install troubleshoot.sh support-bundle CLI in the e2e workflow and
collect cluster diagnostics when tests fail. The bundle is uploaded
alongside existing artifacts for post-failure debugging.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* :seedling: Ensure artifact directory exists before support-bundle collection

Create /tmp/artifacts if it doesn't exist yet, so support-bundle
collection works even when tests fail before writing any artifacts.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>