## Responsive sources
Wire `ensureResponsiveImage` (multi-width × multi-format srcset) into the three
remaining single-`<img>` components:
- ImageBlock (body): widths 600 + 1200, fit follows transform params
- ImageGalleryBlock (single-image branch): widths 600 + 1280, fit=contain
- PostCard (post-list cards): widths 400 + 800, fit=cover, ar=3:2
`resolveContentImages` now sets `block.resolvedResponsive` alongside the legacy
`resolvedImageSrc`, so every Svelte block component renders `<picture>` if
the responsive shape is present and falls back to a plain `<img>` otherwise.
Posts list pages (`/posts`, `/posts/page/N`, `/posts/tag/.../page/N`) call a
new `resolvePostCardResponsive` helper instead of one-shot `ensureTransformedImage`.
## Drop AVIF from defaults
Server-side AVIF encoding on the CMS is 5-10× slower than WebP. The bandwidth
win is marginal for this site and the build time hit is severe (multi-minute
hangs on each new variant). Default formats are now `["webp", "jpeg"]` for
`ensureResponsiveImage`, in `Layout.astro`'s TopBanner hero, and in the
post-card helper. Callers can still opt back into AVIF per-call.
## Module split for client-safe types
`ResponsiveImage` is now defined in a tiny `rusty-image-types.ts` and
duplicated in `rusty-image.ts` so Svelte components can `import type` the
shape without dragging `rusty-image.ts` (and its `node:crypto`/`node:fs`
imports) into the browser bundle.
`resolvePostCardResponsive` lives in a new `server-image.ts` for the same
reason — `blog-utils.ts` is imported by Svelte islands, so its server-only
helpers move out.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Peter Meier