fix(platform): move the zone's startup refusal behind the data seam

check:platform-design holds @sim/logger to lib/data, and the zone's proxy imports
mode.ts, so it gets its own module.

Author: waleedlatif1

apps/sim/platform/docs/org-parity.md

@@ -379,4 +379,4 @@ The shell lane's rows, one per row of its audit. `shell.spec` is `checks/live/sh
 | Per-organization rollout: `platform-org-ui` reaches a targeted organization by id and no other, on the same deployment, through the real AppConfig client against a fixture of its service | `lib/platform/rollout.ts`, `lib/core/config/feature-flags.ts` | Done | "a targeted organization is handed to the Platform", "an organization outside the rollout stays on /o". No real AppConfig deployment has been read. Each route bundle polls on its own clock, so a change can reach the surface API and `/o` up to a poll apart, and until then `/o` can hand off to a zone that answers 404 |
 | A rollback under an open tab: a client navigation keeps working, because the rollout gate lives in a layout that does not re-render, and a reload's 404 offers a way off the zone | `live-shell.tsx`, `lib/data/landing.ts` | Done | "a rollback under an open tab"; `landing.test.ts` for the root's decision. The 404's home button used to loop back to it |
 | Self-hosted, no zone, no flag: boots, `/o` is served by the main app, `/org` is absent | `next.config.ts`, `lib/platform/rollout.ts` | Done | "a self-hosted deployment with no zone boots", "a self-hosted organization is served by the main app", "a self-hosted deployment has no /org", in the `live (flag-off)` job |
-| A production zone behind a base path with no API origin, or on fixtures, refuses to start | `instrumentation.ts`, `lib/data/mode.ts` | Done | "a production zone with no API origin refuses to start", "a production zone on fixtures refuses to start", "a production zone with an API origin starts", each a real `next start` of the build. `instrumentation.ts` exits, because Next only logs a failed `register()` and answers 500 |
+| A production zone behind a base path with no API origin, or on fixtures, refuses to start | `instrumentation.ts`, `lib/data/mode.ts` | Done | "a production zone with no API origin refuses to start", "a production zone on fixtures refuses to start", "a production zone with an API origin starts", each a real `next start` of the build. `lib/data/startup.ts` exits, because Next only logs a failed `register()` and answers 500 |

apps/sim/platform/instrumentation.ts

@@ -1,19 +1,6 @@
-/**
- * Runs when the server starts, so a misconfigured zone never takes a request. Throwing is not enough:
- * Next logs a failed `register()` and keeps the process up answering 500, which a supervisor reads as
- * running. Only exiting fails the deployment.
- */
+/** Runs when the server starts, so a misconfigured zone never takes a request. */
 export async function register() {
   if (process.env.NEXT_RUNTIME !== 'nodejs') return
-  const { assertDeployableMode } = await import('@/platform/lib/data/mode')
-  try {
-    assertDeployableMode()
-  } catch (error) {
-    const [{ createLogger }, { getErrorMessage }] = await Promise.all([
-      import('@sim/logger'),
-      import('@sim/utils/errors'),
-    ])
-    createLogger('PlatformZone').error('Refusing to start', { error: getErrorMessage(error) })
-    process.exit(1)
-  }
+  const { exitUnlessDeployable } = await import('@/platform/lib/data/startup')
+  exitUnlessDeployable()
 }

apps/sim/platform/lib/data/startup.ts

@@ -0,0 +1,20 @@
+import 'server-only'
+import { createLogger } from '@sim/logger'
+import { getErrorMessage } from '@sim/utils/errors'
+import { assertDeployableMode } from '@/platform/lib/data/mode'
+
+const logger = createLogger('PlatformZone')
+
+/**
+ * Stops a misconfigured production zone. Throwing is not enough: Next logs a failed `register()` and
+ * keeps the process up answering 500, which a supervisor reads as running. Only exiting fails the
+ * deployment. Apart from `mode`, because the zone's proxy imports that and has no use for this.
+ */
+export function exitUnlessDeployable() {
+  try {
+    assertDeployableMode()
+  } catch (error) {
+    logger.error('Refusing to start', { error: getErrorMessage(error) })
+    process.exit(1)
+  }
+}