// Package core provides the foundational implementations of the Einherjar
// framework contracts: lifecycle management, structured logging, structured
// errors, and struct validation.
//
// Sub-packages:
//   - launcher — application lifecycle orchestration (init → start → shutdown)
//   - logz     — structured, leveled logging backed by log/slog
//   - xerrors  — typed error codes with context enrichment
//   - valid    — struct validation with pluggable i18n messages
package core