fix: import e2b from rivetkit/sandbox/e2b sub-path

The e2b provider must be imported from rivetkit/sandbox/e2b (sub-path)
rather than rivetkit/sandbox (barrel) because the barrel re-export
would eagerly load all provider dependencies (vercel, modal, etc.)
which aren't installed. Also reverts rivetkit back to fc5f3b4.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

foundry/packages/backend/package.json

@@ -24,7 +24,7 @@
     "drizzle-orm": "^0.44.5",
     "hono": "^4.11.9",
     "pino": "^10.3.1",
-    "rivetkit": "https://pkg.pr.new/rivet-dev/rivet/rivetkit@a6d0f1f",
+    "rivetkit": "https://pkg.pr.new/rivet-dev/rivet/rivetkit@fc5f3b4",
     "sandbox-agent": "workspace:*",
     "uuid": "^13.0.0",
     "ws": "^8.19.0",

foundry/packages/backend/src/actors/sandbox/index.ts

@@ -1,7 +1,8 @@
 // @ts-nocheck
 import { actor, queue } from "rivetkit";
 import { workflow, Loop } from "rivetkit/workflow";
-import { e2b, sandboxActor } from "rivetkit/sandbox";
+import { sandboxActor } from "rivetkit/sandbox";
+import { e2b } from "rivetkit/sandbox/e2b";
 import { existsSync } from "node:fs";
 import Dockerode from "dockerode";
 import { DEFAULT_WORKSPACE_MODEL_GROUPS, workspaceModelGroupsFromSandboxAgents, type WorkspaceModelGroup } from "@sandbox-agent/foundry-shared";

foundry/packages/client/package.json

@@ -16,7 +16,7 @@
   "dependencies": {
     "@sandbox-agent/foundry-shared": "workspace:*",
     "react": "^19.1.1",
-    "rivetkit": "https://pkg.pr.new/rivet-dev/rivet/rivetkit@a6d0f1f",
+    "rivetkit": "https://pkg.pr.new/rivet-dev/rivet/rivetkit@fc5f3b4",
     "sandbox-agent": "workspace:*"
   },
   "devDependencies": {