fix(event-handler): stop recursive HTTP error handler dispatch

[svozza]

Summary

An async error handler rethrowing a matching HTTP error could repeatedly invoke itself, preventing the request from completing and eventually exhausting memory. Error resolution now calls each registered handler at most once per chain and returns the current HTTP error's built-in response when dispatch would revisit a handler.

Changes

• Replace recursive error dispatch with an iterative loop that tracks handler identity locally to each resolution.
• Preserve delegation to different handlers, HTTP status codes and messages, and isolation between concurrent requests.
• Add buffered and streaming regressions for rethrows, fresh error instances, cycles between handlers, shared handlers, and concurrent requests. Twenty regression cases fail against the original implementation.
• Document the fallback behavior and validate types, linting, and unit tests with 100% coverage.

Issue number: closes #5702

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