perf: incremental dev builds + fetchpriority on photo posts

- package.json: add --incremental to dev script (skip unchanged templates)
- post.njk: first photo gets fetchpriority=high instead of loading=lazy
  (first photo is the LCP element on photo post pages)

_includes/layouts/post.njk

@@ -73,7 +73,7 @@ withBlogSidebar: true
       {% if photoUrl and photoUrl[0] != '/' and 'http' not in photoUrl %}
         {% set photoUrl = '/' + photoUrl %}
       {% endif %}
-      <img src="{{ photoUrl }}" alt="{{ img.alt | default('Photo from: ' + title) }}" class="u-photo rounded-lg max-w-full" loading="lazy" eleventy:ignore>
+      <img src="{{ photoUrl }}" alt="{{ img.alt | default('Photo from: ' + title) }}" class="u-photo rounded-lg max-w-full"{% if loop.first %} fetchpriority="high"{% else %} loading="lazy"{% endif %} eleventy:ignore>
     {% endfor %}
   </div>
   {% endif %}

package.json

@@ -6,7 +6,7 @@
   "scripts": {
     "build:og": "node lib/og-cli.js content ${OG_CACHE_DIR:-.cache/og} 'giersig.'",
     "build": "eleventy",
-    "dev": "eleventy --serve --watch",
+    "dev": "eleventy --serve --watch --incremental",
     "build:css": "postcss css/tailwind.css -o css/style.css",
     "check:upstream-widgets": "node scripts/check-upstream-widget-drift.mjs",
     "check:upstream-widgets:strict": "node scripts/check-upstream-widget-drift.mjs --strict",