Context

Add a reader for Cucumber Messages, the newline-delimited JSON format recommended by Cucumber. This enables Allure to read message streams directly alongside the existing Cucumber JSON format.

Closes #79.

Features

• Accepts .jsonl and .ndjson files through the default report reader pipeline.
• Correlates definitions and execution events by their IDs, producing a result for each execution, including interleaved executions and repeated attempts.
• Maps scenario names, descriptions, feature and tag labels, outline parameters, source-based full names, and step names with Gherkin keywords.
• Preserves scenario timestamps and measured step/hook durations in milliseconds.
• Converts explicitly typed before/after scenario hooks into fixtures. Hooks without a type are represented as named steps.
• Supports base64-encoded and plain-text execution attachments, doc strings with their declared media types, and data tables as CSV attachments.
• Copies supplied error messages and stack traces directly. Status mapping follows the Cucumber JSON reader: PASSED/FAILED map directly, SKIPPED/PENDING become skipped, UNDEFINED/AMBIGUOUS become broken, and unknown statuses or unfinished executions remain unknown.
• Ignores unsupported envelope types and reports parsing failures through the standard reader interface.

The implementation uses local schema types and existing reader APIs, with no new external dependencies. Allure core handles test/history identities and standard label processing.

Checklist

• Sign Allure CLA
• Provide unit tests