feat(cli): introduce user-facing error presentation - #221

Allow classified errors to carry optional caller-owned user-facing messages without changing their technical diagnostics, failure classes, exit codes, or structured error metadata.

Render explicit presentations after redaction without fallback headers, guidance, or additional styling, while retaining the existing fallback for current command mappings. Add per-call control over the logger stderr sink so explicit presentations suppress only duplicate logger output while tracing and file persistence remain active. Keep logger persistence and retention failures fail-open, and update the associated runtime contracts and context documentation.

Co-authored-by: SCE <sce@crocoder.dev>

Present concise login guidance when sync encounters typed missing or failed
control-plane authentication while retaining the classified runtime error.
Document the rendering contract and updated command behavior.

Co-authored-by: SCE <sce@crocoder.dev>