Harden skills with CLI checks, timeouts, and parallel execution

[schmug]

• Add CLI availability verification (command -v) as first step in all
  skills, with actionable install instructions on failure
• Wrap all external CLI calls with timeout 120 to prevent indefinite hangs
• Use mktemp for codex temp files instead of fixed /tmp paths to avoid
  race conditions with concurrent invocations
• Explicitly instruct /second-opinion to run Gemini and Codex queries as
  parallel Bash tool calls for ~2x faster wall-clock time
• Improve context gathering guidance: structured prompt format with
  labeled code blocks, stdin piping for large context
• Handle missing config files gracefully (check existence before reading)
• Add graceful degradation to /second-opinion when only one CLI is available

https://claude.ai/code/session_01PVhFi3d3ptmxtHPCCdxu8A