When claw --output-format json --resume <session> /commit (or /plugins, etc.)
encountered an 'unsupported resumed slash command' error, it called
eprintln!() and exit(2) directly, bypassing both the main() JSON error
handler and the output_format check.
Fix: in both the slash-command parse-error path and the run_resume_command
Err path, check output_format and emit a structured JSON error:
{"type":"error","error":"unsupported resumed slash command","command":"/commit"}
Text mode unchanged (still exits 2 with prose to stderr).
Addresses the resumed-command parity gap (gaebal-gajae ROADMAP #26 track).
159 CLI tests pass, fmt clean.
da4242198f