Make zombie children clean themselves up

The parent wds process can crash sometimes when watching too many files, or due to memory pressure on the system, or really any number of reasons. When this happens, the children become zombies and live forever. If the parent crashes though, they'll never be reloaded, and signals from the terminal won't be sent along to them, so they just accumulate and suck up memory on developer machines! Yuck!

This adds active monitoring to the child wds processes so that they notice if the parent is gone, and kill themselves right away if so. This isn't 100% reliable, but this will at least reap most of em so we stop accumulating so much cruft.

package.json

@@ -61,7 +61,8 @@
     "gitpkg": "^1.0.0-beta.2",
     "jest": "^27.4.7",
     "prettier": "^2.8.8",
-    "typescript": "^5.1.3"
+    "typescript": "^5.1.3",
+    "zx": "^7.2.3"
   },
   "packageManager": "pnpm@8.12.1+sha256.28ca61ece5a496148b73fabc9afb820f9c3fec4f55f04ce45a2cea0a5219f2e1"
 }