@thexjs/core@1.2.0

Minor Changes

• fbd5e29: Extract the platform-agnostic adapter pipeline (build-manifest resolution,
  per-file transpile, standalone render-function bundling, entry generation)
  into @thexjs/core/adapter as a documented Adapter SDK. @thexjs/adapter-vercel
  now composes the SDK (adding only its Node<->Web Request/Response bridge and
  Build Output API v3 .vercel/output tree), so third-party adapters (Node,
  Cloudflare, ...) reuse the same build core instead of reverse-engineering it.

  @thexjs/adapter-vercel now requires @thexjs/core@^1.2.0 (the release that
  introduces the @thexjs/core/adapter subpath) so consumers can never resolve
  the adapter against an older core that lacks the SDK export.

  Also hardened the generated Vercel entry: forwarded headers (x-forwarded-proto
  / x-forwarded-host) are validated instead of blindly trusted, streamed
  responses honor socket backpressure and cancel on client disconnect, the error
  path guards against already-sent headers, generated paths are project-relative,
  and non-JSON-serializable runtime options fail the build instead of silently
  dropping (keeping the deployed function aligned with x start).

• 58aa123: Add production-grade observability metrics: createInMemoryMetrics() (an in-process registry serving /metrics in Prometheus text format), createOtlpMetricsReporter() (forwards counters/histograms to an OpenTelemetry meter), and withRequestMetrics(). When passed as observability.metrics to createApp, every request records x_http_requests_total, x_http_request_duration_ms, and x_http_errors_total (plus x_rate_limit_rejections_total), and a /metrics endpoint is served ahead of routing when the reporter exposes one.