feat(sacred-valley): masonry card layout — content-height row spans + dense flow

Cards keep their column span but now span grid rows proportional to
measured content height (ResizeObserver re-packs async cards), with
grid-auto-flow: dense. Fixes mismatched sizes / rigid rows / vertical gaps.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "void-server",
-  "version": "2.6.6",
+  "version": "2.7.0",
   "type": "module",
   "private": true,
   "scripts": {