Create Evlog Enricher

You need to add a new enricher to evlog's built-in collection, and this walks you through all six mandatory touchpoints: source code, tests, built-in docs, overview cards, skill reference, and the README table. The architecture is strict (info interface, factory function, header lookup, field merging with overwrite flags), so having a checklist and naming conventions in hand saves you from forgetting the test suite or leaving the docs half-done. It's built on the same `defineEnricher` primitive that community enrichers use, which keeps the shape consistent. If you've ever scaffolded a plugin by hand and missed updating the export map or forgot edge case tests, this is that checklist turned into automation.