## 1. CSS shimmer styles

- [x] 1.1 Add `@keyframes shimmer` animation to `global.css` — a translucent gradient sweep (left-to-right) that works on the dark theme background (`--bg0`/`--bg1` palette).
- [x] 1.2 Add `.img-shimmer-wrap` class to `global.css` — `position: relative; overflow: hidden;` container that inherits dimensions from its parent. Add a `::before` pseudo-element with the shimmer animation (full width/height, absolute positioned, translucent light gradient).
- [x] 1.3 Add `.img-loading` class to `global.css` — sets `opacity: 0` on the `<img>` element. Add transition: `opacity 250ms ease`.
- [x] 1.4 Add `.img-error` class to `global.css` — stops the shimmer animation on the wrapper (`animation: none` on `::before`) so the placeholder displays as a static block.
- [x] 1.5 Verify the existing `@media (prefers-reduced-motion: reduce)` rule in `global.css` already suppresses the shimmer `@keyframes` animation (it should — the global rule sets `animation-duration: 0.001ms !important`).

## 2. Card thumbnail shimmer

- [x] 2.1 Update `StandardCard.astro` — wrap the existing `<img>` in a `<div class="img-shimmer-wrap">`. Add class `img-loading` to the `<img>` element. Keep the existing `.card-placeholder` fallback for cards with no image (no shimmer needed there).
- [x] 2.2 Ensure the `.img-shimmer-wrap` inside `.card-media` inherits the correct dimensions (`width: 100%; height: 180px` on desktop, `200px` on mobile) without causing layout shift.

## 3. Blog featured image shimmer

- [x] 3.1 Update `blog/post/[slug].astro` — wrap the featured `<img>` in a `<div class="img-shimmer-wrap">` with matching inline styles (`width: 100%; max-height: 420px; border-radius: 16px; overflow: hidden;`). Add class `img-loading` to the `<img>`.
- [x] 3.2 Update `blog/page/[slug].astro` — same shimmer wrapper treatment as blog posts.

## 4. Image load/error script

- [x] 4.1 Add an inline `<script is:inline>` in `BaseLayout.astro` (or a shared location) that runs on DOM ready. For every `img.img-loading` element: if `img.complete && img.naturalWidth > 0`, remove `img-loading` immediately (cached images). Otherwise, add `load` event listener to remove `img-loading` and `error` event listener to add `img-error` to the wrapper.
- [x] 4.2 Verify the script handles dynamically added images (not currently needed — SSG renders all images server-side — but ensure the script runs after all DOM is ready).

## 5. Verification

- [x] 5.1 Run `npm run build` in `site/` and verify no build errors.
- [x] 5.2 Run `npm test` in `site/` and verify all existing tests pass (1 pre-existing failure in blog-nav.test.ts unrelated to this change — expects `/about` nav link that doesn't exist).
- [x] 5.3 Manual smoke test: throttle network in DevTools (Slow 3G), load homepage — verify shimmer appears on card thumbnails, images fade in on load.
- [x] 5.4 Manual smoke test: load a blog post with a featured image on throttled network — verify shimmer and fade-in.
- [x] 5.5 Manual smoke test: break an image URL temporarily — verify static placeholder shows (no broken image icon, no infinite shimmer).
- [x] 5.6 Manual smoke test: enable `prefers-reduced-motion: reduce` in browser/OS settings — verify shimmer animation is suppressed (static placeholder, no sweep).
- [x] 5.7 Verify no cumulative layout shift: compare card dimensions before and after the change using DevTools Layout Shift overlay.

Note: Tasks 5.3–5.7 require manual browser testing with DevTools network throttling.
