test(e2e): scope the last global Stalker reset in sources-pwa helpers

Completes 3a93fef0f: that commit scoped self-hosted.e2e.ts but missed
resetPwaMockServers, which still wiped the whole Stalker fixture from a
third spec file. Scope it to the two MACs this suite owns.

The auth tests use dedicated MACs no sibling touches, so portal sessions
— the fragile state — can no longer be cleared by a parallel worker.
Content MACs still overlap between files, which is harmless: that data is
regenerated deterministically from the same seed.

Verified with the full interfering set running together:
stalker.e2e.ts + self-hosted.e2e.ts + sources-pwa.e2e.ts, 26/26 green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

apps/web-e2e/src/sources-pwa.helpers.ts

@@ -31,11 +31,25 @@ type SourceDialogField =
     | 'title'
     | 'username';
 
+/**
+ * Reset the fixtures this suite uses. The Stalker reset is scoped to the MACs
+ * touched here: that mock is shared with stalker.e2e.ts, which runs in a
+ * parallel Playwright worker, and a global reset would destroy its portal
+ * sessions mid-test.
+ */
 export async function resetPwaMockServers(
     request: APIRequestContext
 ): Promise<void> {
     await request.post(`${XTREAM_MOCK_SERVER}/reset`);
-    await request.post(`${STALKER_MOCK_SERVER}/reset`);
+    await Promise.all(
+        [DEFAULT_MAC, EDITED_MAC].map((mac) =>
+            request.post(
+                `${STALKER_MOCK_SERVER}/reset?macAddress=${encodeURIComponent(
+                    mac
+                )}`
+            )
+        )
+    );
 }
 
 export async function interceptPwaProviderRequests(