test(web): register the sidebar scrollbar e2e on the host plane

Every scaffold-importing e2e compiles on the host plane, so the new file
goes in tsconfig.host.json's include list and apps/web/tsconfig.json's
exclude list. Without both, tsc -p apps/web/tsconfig.json fails with
TS6059/TS6307.

tsconfig.host.json

@@ -19,6 +19,7 @@
     "apps/web/tests/workspace-management.e2e.ts",
     "apps/web/tests/replay-round-trip.e2e.ts",
     "apps/web/tests/seeded-history.e2e.ts",
+    "apps/web/tests/sidebar-scrollbar.e2e.ts",
     "apps/web/tests/code-mode-round.e2e.ts",
     "apps/web/tests/cordis-tool-round.e2e.ts",
     "apps/cli/tests/**/*.ts",