New candidate entered a pipeline

Fires the moment a Candidate row is created in the database —
whether they applied through the public application form, were
sourced via the public API, or pulled in from an ATS sync (Ashby
/ Greenhouse). The payload carries the full Candidate DTO and
a summary of the pipeline they applied to, so receivers can act
without an extra GET /pipelines/:id round-trip.

Fires before any candidate.stage_changed events the pipeline's
automation graph emits — receivers can rely on applied
preceding any node-transition events for the same candidate.