chore: add sentry events for state splitting migration (#38978)

## **Description**

Example:
https://metamask.sentry.io/insights/frontend/summary/events/?project=273496&query=tags%5Btransaction%5D%3Atask%2FmigrateToSplitState&sort=-timestamp&statsPeriod=1h&transaction=task%2FmigrateToSplitState

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<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Adds observability around split-state migration.
> 
> - New `utils/run-tracked-task.ts` helper starts a Sentry span
(`task/<name>`), sets status, tags errors, captures exceptions, and
rethrows
> - Wraps `PersistenceManager.migrateToSplitState` in
`runTrackedTask('migrateToSplitState', ...)`; migration logic unchanged
aside from tracing
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
a1ac9bf. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: davidmurdoch

app/scripts/lib/stores/persistence-manager.ts

@@ -11,6 +11,7 @@ import type {
   BaseStore,
   MetaData,
 } from './base-store';
+import { runTrackedTask } from './utils/run-tracked-task';
 
 export type StorageKind = 'data' | 'split';
 
@@ -568,29 +569,33 @@ export class PersistenceManager {
    * occur.
    */
   async migrateToSplitState(state: MetaMaskStateType) {
-    if (this.storageKind === 'split') {
-      log.debug('[Split State]: Storage is already split, skipping migration');
-      return;
-    }
+    return runTrackedTask('migrateToSplitState', async () => {
+      if (this.storageKind === 'split') {
+        log.debug(
+          '[Split State]: Storage is already split, skipping migration',
+        );
+        return;
+      }
 
-    if (!this.#metadata) {
-      throw new Error(
-        'MetaMask - metadata must be set before calling "migrateToSplitState"',
-      );
-    }
+      if (!this.#metadata) {
+        throw new Error(
+          'MetaMask - metadata must be set before calling "migrateToSplitState"',
+        );
+      }
 
-    this.storageKind = 'split';
-    const metadata = structuredClone(this.#metadata);
-    metadata.storageKind = 'split';
-    this.setMetadata(metadata);
-    for (const [key, value] of Object.entries(state)) {
-      this.update(key, value);
-    }
+      this.storageKind = 'split';
+      const metadata = structuredClone(this.#metadata);
+      metadata.storageKind = 'split';
+      this.setMetadata(metadata);
+      for (const [key, value] of Object.entries(state)) {
+        this.update(key, value);
+      }
 
-    // mark data key for deletion
-    this.update('data', undefined);
+      // mark data key for deletion
+      this.update('data', undefined);
 
-    log.debug('[Split State]: Migrating to split state storage');
-    await this.persist();
+      log.debug('[Split State]: Migrating to split state storage');
+      await this.persist();
+    });
   }
 }

app/scripts/lib/stores/utils/run-tracked-task.ts

@@ -0,0 +1,58 @@
+import type * as Sentry from '@sentry/browser';
+
+const sentry = globalThis.sentry as typeof Sentry | undefined;
+
+export async function runTrackedTask<Return>(
+  taskName: string,
+  fn: () => Promise<Return>,
+): Promise<Return> {
+  if (!sentry) {
+    return fn();
+  }
+
+  const attributes = {
+    'task.name': taskName,
+  };
+
+  return sentry.startSpan(
+    {
+      name: `task/${taskName}`,
+      op: 'task',
+      forceTransaction: true,
+      attributes,
+    },
+    async (span) => {
+      try {
+        const result = await fn();
+
+        span.setStatus({ code: 1 });
+
+        return result;
+      } catch (err) {
+        span.setStatus({
+          code: 2, // 2 === SPAN_STATUS_ERROR
+          message: 'internal_error',
+        });
+        span.setAttribute(
+          'task.error_message',
+          err instanceof Error ? err.message : String(err),
+        );
+
+        // Creates an *error event* (Issue), separate from the span.
+        sentry.captureException(err, {
+          tags: { 'task.name': taskName, 'task.status': 'failed' },
+        });
+
+        // rethrow the error after capturing it so the process crashes, as
+        // we can't know how to recover from here. This will result in the
+        // exception being captured by sentry _again_ by the global error
+        // handler, and that's fine. We capture here because we want to add this
+        // taskName tag to the error event so we can easily find and filter it
+        // later. All this is sentry tracking code in here is temporary until we
+        // are confident that the migration code is stable enough, and we can
+        // roll it out to 100%.
+        throw err;
+      }
+    },
+  );
+}