Summary

• Fixes silent error absorption in injectRSCPayload.ts where three error handlers (htmlStream.on('error', () => {}), catch {} in startRSC, and .catch(() => endResultStream())) swallowed errors, preventing them from reaching errorReporter/Sentry
• Introduces a shared safePipe utility that replaces the scattered pipe+close boilerplate with a single function handling the Node.js pipe() gap (destination not ended on source destroy) and optional onError callback for non-fatal error reporting
• Fixes a missed pipe site in transformRSCNodeStream.ts that PR Fix streaming SSR hangs and silent error absorption in RSC payload injection #2407 did not cover

How it works

Errors emitted on resultStream inside injectRSCPayload propagate through safePipe's onError at the pipeToTransform site → emitError() → readableStream → handleStreamError → errorReporter. The pipe stays intact, data continues flowing, and Fastify never sees the errors.

Test plan

• injectRSCPayload.test.ts — 7 tests pass
• streamServerRenderedReactComponent.test.jsx — 16 tests pass
• RSCRequestTracker.test.ts — 8 tests pass
• streamBackpressure.e2e.test.tsx — 4 tests pass
• handleStreamError.test.ts — 6 tests pass
• streamErrorHang.test.ts — 3 tests pass
• ESLint passes with 0 errors
• Prettier formatting clean
• TypeScript compilation clean

Closes #2450

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