fix: remove duplicate OG image generation in build script

build:og was running before eleventy, then eleventy.before ran it again —
two full generation passes per build. Since eleventy.before handles OG
generation, the standalone pre-step is redundant.

Also fix build:og path: was passing .cache (parent dir) which after the
ogDir rename wrote PNGs to the wrong location. Now uses OG_CACHE_DIR env
var with .cache/og as fallback, matching eleventy.config.js behaviour.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -4,8 +4,8 @@
   "description": "Eleventy theme for Indiekit — IndieWeb-ready personal website",
   "type": "module",
   "scripts": {
-    "build:og": "node lib/og-cli.js content .cache 'giersig.'",
-    "build": "npm run build:og && eleventy",
+    "build:og": "node lib/og-cli.js content ${OG_CACHE_DIR:-.cache/og} 'giersig.'",
+    "build": "eleventy",
     "dev": "eleventy --serve --watch",
     "build:css": "postcss css/tailwind.css -o css/style.css",
     "check:upstream-widgets": "node scripts/check-upstream-widget-drift.mjs",