v0.5.5

Fixes

• No more stderr noise: SilenceErrors + SilenceUsage on root command. Errors go exclusively through the JSON envelope on stdout.
• Non-zero exit codes: All error paths return proper exit codes via output.PrintFail(). No more exit 0 on failures.
• HTTP timeout on update check: 5s timeout prevents CLI hangs when GitHub API is slow or unreachable.
• Download timeout: Binary downloads use 60s timeout.

Internal

• New output.PrintFail() and output.ExitError helpers
• 16 command files refactored from Print+return nil to return PrintFail()
• Test mock client updated to cover custom HTTP clients