[ehsanmsb]

Summary

• Fetch and refresh multiple published MkDocs search indexes independently.
• Search all sites with one BM25 corpus, unique page IDs, site labels, and an optional site filter.
• Keep the last good content when a site refresh fails and report partial availability.
• Update Helm configuration, usage docs, and multi-site tests.

Validation

• Ruff, mypy, 24 pytest tests, and Helm lint passed.
• A local end-to-end run loaded three published MkDocs sites and verified search, page lookup, UI, readiness, and source links.

The live test site URLs are configuration only; they are not hardcoded in the repository.