fix(ci): add typescript as explicit devDependency

pnpm strict hoisting means only direct deps are on PATH. The overrides
entry pins the version but does not install tsc as a binary. Without an
explicit devDependency entry pnpm run tsc fails with "tsc: not found".

package.json

@@ -73,6 +73,7 @@
     "react-dom": "^18.3.1",
     "react-router-dom": "^5.3.0",
     "typedoc": "^0.28.16",
+    "typescript": "~5.6.2",
     "typedoc-plugin-markdown": "^4.10.0",
     "vitest": "^3.2.4"
   }