chore: add changeset for workflow bundler migration

Author: ryanwaits

.changeset/workflow-bundler-migration.md

@@ -0,0 +1,13 @@
+---
+"@secondlayer/api": minor
+"@secondlayer/sdk": minor
+"@secondlayer/web": patch
+---
+
+Move workflow bundling from Vercel to the Hetzner API.
+
+- **API**: new `POST /api/workflows/bundle` route that accepts a TypeScript workflow source, runs `bundleWorkflowCode` from `@secondlayer/bundler`, and returns the bundled handler + extracted metadata. Mapped via the existing `/api/workflows/*` auth + rate-limit middleware. `BundleSizeError` → `HTTP 413`, other failures → `HTTP 400`. Logs every request with `x-sl-origin` + `bundleSize` for telemetry parity with deploy logs.
+- **SDK**: new `workflows.bundle({ code })` method plus `BundleWorkflowResponse` type.
+- **Web**: `POST /api/sessions/bundle-workflow` rewritten as a thin direct-fetch passthrough to the Hetzner API. `@secondlayer/bundler` is no longer a dependency of `apps/web` and `esbuild` is no longer in `serverExternalPackages`. Vercel cold starts drop esbuild's native binary from the hot path. CLI and MCP continue to bundle locally — this only affects the chat authoring loop.
+
+This fixes a class of `"Module evaluation failed: Cannot find module 'unknown'"` / `NameTooLong` / `Could not resolve "@secondlayer/workflows"` failures that kept surfacing when esbuild ran inside Vercel serverless functions. Chat deploy flow now goes Vercel → Hetzner `/api/workflows/bundle` → Hetzner `/api/workflows` → workflow-runner, all against stable workspace layouts.