mcp info, mcp describe, and mcp list-filter all return
{"action":"error","ok":false,...} but previously exited 0,
requiring automation callers to inspect the envelope field.
After this fix: print_mcp detects ok:false in the rendered JSON
value and calls process::exit(1) after printing, so the exit code
reflects the semantic error in the envelope.
Unaffected: mcp list, mcp show, mcp help all have no ok field and
continue to exit 0 (they are not error paths).
Closes ROADMAP #68 (partial — agents bogus/mcp show nonexistent
found:false remain exit:0 as they use different envelope shapes).
64f92b1560