Fix sed syntax error in convert_ipynb_to_org.sh

Added missing closing delimiter '/' to sed substitution command.
The pattern 's/^%/#%' was missing the final '/' which caused
"unterminated substitute in regular expression" error on macOS.

Fixed on both Darwin and Linux branches.

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

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

Author: ElleNajt

bashscripts/convert_ipynb_to_org.sh

@@ -76,11 +76,11 @@ convert_file() {
         if [[ "$(uname -s)" == "Darwin" ]]; then
             sed -i '' '/^<<.*>>$/d' "$org_file"
             sed -i '' '/:PROPERTIES:/,/:END:/d' "$org_file"
-            sed -i '' 's/^%/#%' "$org_file"
+            sed -i '' 's/^%/#%/' "$org_file"
         else
             sed -i '/^<<.*>>$/d' "$org_file"
             sed -i '/:PROPERTIES:/,/:END:/d' "$org_file"
-            sed -i 's/^%/#%' "$org_file"
+            sed -i 's/^%/#%/' "$org_file"
         fi
     fi