observability: backend-agnostic error-capture seam (Phase 1, inert until SENTRY_DSN)

instrumentation.ts

@@ -0,0 +1,27 @@
+// Next.js instrumentation. `onRequestError` is the framework-wide hook that
+// fires for any error thrown out of a route handler, server component, or
+// server action -- so it is the broad net that gives every server action
+// error capture without per-action wiring. Swallowed best-effort failures
+// (notification fan-outs, cron soft-fails, the Stripe handler that returns 500
+// instead of throwing) do NOT reach this hook, so those are captured manually
+// at their sites. Inert until SENTRY_DSN is set (the seam no-ops).
+import { captureException } from '@/lib/observability/capture'
+
+export async function register(): Promise<void> {
+  // No global init: the capture seam is a stateless fetch transport.
+}
+
+export async function onRequestError(
+  err: unknown,
+  request: { path?: string; method?: string },
+  context: { routerKind?: string; routePath?: string; routeType?: string },
+): Promise<void> {
+  captureException(err, {
+    surface: 'request',
+    tags: {
+      route: context?.routePath,
+      routeType: context?.routeType,
+      method: request?.method,
+    },
+  })
+}