Rename MuJoCo WASM output artifacts to mujoco.*.

This change updates the Emscripten build to output files named `mujoco.js`, `mujoco.wasm`, and `mujoco.d.ts` instead of `mujoco_wasm.*`. The internal CMake target name remains `mujoco_wasm` to avoid conflicts. The package name in `package.json` is also updated to `mujoco`. New enum tests are added.

PiperOrigin-RevId: 875140314
Change-Id: Ie03e0d1db2d03dd8582d5bfcb260b3d33549c2c9

wasm/package-lock.json

@@ -1,11 +1,11 @@
 {
-  "name": "mujoco_wasm",
+  "name": "mujoco",
   "version": "1.0.0-alpha.1",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
-      "name": "mujoco_wasm",
+      "name": "mujoco",
       "version": "1.0.0-alpha.1",
       "license": "Apache-2.0",
       "devDependencies": {