zagent 0.0.230

• --json error paths now emit the JSON error envelope on stdout instead
  of failing silently: -p --json credential and no-runtime gates print
  the envelope (num_turns: 0, human card stays on stderr, exit codes
  unchanged), and quota --json failure/usage/refusal paths print
  {"error": ...}. zagent sessions on a fresh install no longer warns
  about an absent tasks index.
• zagent goal list [--all] [--json] enumerates sessions from the task
  index (read-only; empty state prints no sessions and points at
  goal show --session <id>); zagent plugins list is now a verb
  (previously treated list as a plugin name); a bare zagent mcp on a
  TTY or empty stdin prints usage guidance and exits 2 instead of
  exiting 0 silently.
• Privacy: paths under the user's home directory now render as ~/...
  in doctor, import (human + JSON), inspect, the TUI /doctor and
  /status mirrors, and -p error output — no more absolute home paths
  in copied output (flock findings F7/F12).