Set projectRoot to null explicitly

This is important because if we don't send it explicitly and just
leave it out, it defaults to the current working directory.

Generally speaking, this will result in all stack frames from the
CLI being identified as outside of the project, preventing correct
error grouping in Observe.

By setting an explicit null project root, we prevent the SDK-side
assignment of in-project state, and we fall back to Observe's
much smarter algorithm for identifying in-project lines.

For context, see https://github.com/bugsnag/bugsnag-js/blob/286caed5daae9349be8fb22ab0051204bfc1a813/packages/plugin-node-in-project/in-project.js

Author: amcaplan

packages/cli-kit/src/public/node/error-handler.ts

@@ -283,5 +283,10 @@ function initializeBugsnag() {
       notify: 'https://error-analytics-production.shopifysvc.com',
       sessions: 'https://error-analytics-sessions-production.shopifysvc.com',
     },
+    // Set the project root to `null` to prevent the default behavior of
+    // Bugsnag which is to set it to the cwd. That is unhelpful for us because
+    // the cwd can be anywhere in the user's filesystem, not necessarily
+    // related to the CLI codebase.
+    projectRoot: null,
   })
 }