Replace manual format detection (printf "%T", MediaType.SubType whitelists,
duck-typing) with Hugo's new reflect.IsResource, reflect.IsImageResource, and
reflect.IsImageResourceProcessable functions across 19 template files.
Key changes:
- process_responsive_image: collapse 15-line format whitelist into single
reflect.IsImageResourceProcessable call
- Unify three-way SVG/processable/GIF branches into two-way $canProcess guard
- Remove duplicate GIF passthrough branches in single.html, events/page.html
- Add missing SVG guard in research-areas block (was calling .Fill unprotected)
- Replace nil checks with reflect.IsResource in get_cover_image/get_featured_image
Design decision: GIFs are intentionally excluded from processing despite Hugo
supporting it — processing strips animation frames, so we preserve user-optimized
animated GIFs by checking (IsImageResourceProcessable AND not GIF).
SVG resources don't support .Width, .Height, or .Process in Hugo,
causing crashes in process_responsive_image.html and all callers
that pass SVGs without guards.
Add SVG checks to process_responsive_image.html, preact-wrapper.html,
resume-biography, resume-biography-3, authors/term, and
page_author_card.
Fixes#3305
George Cushen