refactor: Replace Rollup with Vite (#2656)

This is a high risk change: every byte the card ships is emitted by a
different bundler, minified by a different minifier, and every
stylesheet is compiled by a different sass. The intent is that the
card's behaviour is unchanged.

**Significant development win**: Build time drops from 24s to 1.1s 🎉 

Also adds a test suite ('dist') that runs against the built bundle.

.claude/settings.json

@@ -8,7 +8,7 @@
       "Bash(yarn prettier *)",
       "Bash(npx tsc --noEmit *)",
       "Bash(npx eslint *)",
-      "Bash(npx rollup -c *)",
+      "Bash(npx vite build *)",
       "Read(~/.claude/projects/**)"
     ]
   }