fix(plugins): declare typescript devDep so tsc builds don't rely on hoisted root

Each plugin package invokes `tsc` in its build script but previously relied on
a root-hoisted typescript. When the root symlink breaks (e.g. after switching
worktrees that shared a pnpm store), `pnpm -r build` fails with MODULE_NOT_FOUND
for tsc — blocking `pnpm dev dashboard`. Declaring typescript locally makes
each plugin self-sufficient.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

plugins/examples/fusion-plugin-settings-demo/package.json

@@ -22,6 +22,7 @@
   },
   "devDependencies": {
     "@types/node": "^25.5.2",
+    "typescript": "^5.7.0",
     "vitest": "^3.2.4"
   }
 }