chore: pin @emnapi/* as optional deps to fix npm ci

Workaround for the npm optional-deps lockfile bug triggered by
@tailwindcss/oxide-wasm32-wasi and @rolldown/binding-wasm32-wasi
(both pull in @napi-rs/wasm-runtime which peer-depends on @emnapi/*).

Without this, npm ci fails on platform switches (Linux <-> macOS,
arm64 <-> x64) because the lockfile drops the WASM-fallback peer
entries depending on which platform generated it.

Refs: npm/cli#4828

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

Author: kevinccbsg

package-lock.json

@@ -59,5 +59,9 @@
     "vite": "^8.0.10",
     "vite-plugin-istanbul": "^8.0.0",
     "vitest": "^4.1.5"
+  },
+  "optionalDependencies": {
+    "@emnapi/core": "^1.10.0",
+    "@emnapi/runtime": "^1.10.0"
   }
 }