Replace direct fmt.Fprintf(os.Stderr, "Error:...") + os.Exit(1) patterns with FatalError() and FatalErrorWithHint() helpers for consistent error handling. Files updated: - compact.go: All 48 os.Exit(1) calls converted - sync.go: All error patterns converted (kept 1 valid summary exit) - migrate.go: Partial conversion (4 patterns converted) This is incremental progress on bd-qioh. Remaining work: ~326 error patterns across other cmd/bd files. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>