Create reveal.js 5.x slide deck for 'Call the Doctor' HDF Group stream

[steven-varga]

Prepare a small talk for the HDF Group 'Call the Doctor' stream to present recent H5CPP changes.

Goals

• Scaffold with reveal.js 5.x (modern, not the legacy v3.x copy-paste pattern).
• Keep content Markdown-first.
• Reference a shared core to avoid the duplication tax seen in existing decks under \docs/slides/.
• Content: summarise H5CPP changes from release → staging (type engine, filtering pipeline, linalg adapters, CI maturation).

Acceptance Criteria

• New deck directory under \docs/slides/\ (or a new shared layout).
• Works with ?print-pdf\ for export.
• Deployable to the existing S3/GitHub Pages pipeline.