Add prebuild script to copy videos from submodule

Copies mp4 files from src/content/writing/images/ to public/images/
so that video embeds in articles work correctly.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: meaningfool

.gitignore

@@ -1,6 +1,9 @@
 # build output
 dist/
 
+# copied assets from submodule (generated by prebuild)
+public/images/*.mp4
+
 # generated types
 .astro/
 

package.json

@@ -7,6 +7,7 @@
   },
   "scripts": {
     "dev": "astro dev",
+    "prebuild": "mkdir -p public/images && cp src/content/writing/images/*.mp4 public/images/ 2>/dev/null || true",
     "build": "astro build",
     "preview": "astro preview",
     "astro": "astro"