fix(next): route global drain through next after() to survive prerender

[evlogai]

Summary

Fixes #654. The global log.* drain configured in createInstrumentation started inline in the emitting context. During Next Cache Components prerender, the prerender pass rejects in-flight work when it completes, so the fire-and-forget drain fetch() could be cancelled mid-send (HANGING_PROMISE_REJECTION) and adapters logged Failed to send events.

The fix wraps the global drain so its work is deferred through Next's after(): the event is emitted synchronously, but the drain runs in a post-response context that outlives the prerender pass.

Changes

• packages/evlog/src/next/instrumentation-create.ts
  • resolveAfter(): dynamically imports after from next/server, caches the result, and returns null when unavailable (older Next versions, or an import failure), so nothing breaks outside Cache Components apps.
  • createLifecycleSafeDrain(): wraps the configured drain; when after resolves, the drain invocation is submitted to after(...) instead of running inline. Falls back to the previous inline behavior when after is missing or after() throws synchronously.
  • register() wires the wrapped drain as config.drain.
• Regression test in packages/evlog/test/next/instrumentation-drain.test.ts covering three modes: after available (drain deferred, delivered from the after callback), after throwing (inline fallback), after missing (inline fallback).
• Existing instrumentation.test.ts delegation assertion updated for the wrapper.
• Changeset: evlog patch.

Checks

• pnpm run lint: pass
• pnpm run typecheck: pass
• pnpm run test: pass (all workspace packages, evlog next suite 80/80)
• Regression test verified red before the fix (1 failed / 2 passed) and green after (3 passed), see evidence below.

Scope notes (honest limitations)

• The literal repro shape from the issue (a plain log.info in a prerendered Server Component) fails earlier with this package version: isoNow() calls Date.now(), which Next rejects during prerender (unstable value 'Date.now()'). The drain-cancellation path was reached via a PPR-shaped page ("use cache" + uncached fetch in <Suspense>).
• On next 16.3.4 + evlog 2.28.1 with next start, the HANGING_PROMISE_REJECTION could not be reproduced end-to-end locally; runtime smoke tests showed successful delivery both before and after the fix. The deferral is proven by the unit tests, which exercise the actual wiring.
• register() (instrumentation) does not run in next build prerender workers, so build-time prerender remains unaffected; the fix targets the runtime request path.

Visual evidence

Before (main): the regression test fails, the drain starts inside the emitting context.

After (this branch): the drain is deferred through after() and delivered from the post-response context.

Before	After

[vercel]

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Project	Deployment	Actions	Updated
evi	Ready	Preview	Sep 3, 2026 10:11pm UTC
evlog-docs	Ready	Preview, v0	Sep 3, 2026 10:11pm UTC
evlog-render-lab	Ready	Preview	Sep 3, 2026 10:11pm UTC
evlog-telemetry	Ready	Preview	Sep 3, 2026 10:11pm UTC
just-use-evlog	Error		Sep 3, 2026 10:11pm UTC

[github-actions]

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commit: d61ba1e