Problem

v0.1 delivers baseline file+line errors. v1.0 requires production-grade error UX: structured machine-readable output, extended explanations, and recovery suggestions.

Acceptance Criteria

• --json flag on all commands outputs structured error objects (code, file, line, col, message)
• nlsc explain E001 (or --explain flag) gives extended documentation for each error code
• Every error class has a documented error code
• Recovery hints are context-aware (e.g. suggests correct @use path, correct type name)
• Editor/LSP integration can consume structured errors

Why This Blocks v1.0

Production tools have production error handling. This is a trust signal for engineering teams.