Add adversarial-verification plugin

[wizardengineer]

Summary

Adds a new adversarial-verification plugin that stress-tests claims, designs, and bug findings by dispatching two isolated sub-agents (advocate + skeptic) and synthesizing their arguments into a structured verdict. Counters sycophancy and single-agent agreement bias by forcing maximal disagreement before the caller commits.

What it does

Two modes:

• Decision mode — free-form arguments organized by evaluation dimensions (for approach/design choices)
• Proof mode — N null hypotheses the skeptic tries to prove and the advocate tries to refute (for verifying bug findings and security claims)

Core principle: isolated sub-agent contexts are non-negotiable. An agent that sees the other side's arguments will soften to accommodate them. The adversarial value comes from each agent arguing without knowledge of the counter-argument, with synthesis happening separately.

Structure

• SKILL.md (main entry point with decision tree for mode selection)
• references/decision-mode.md (structure for approach selection)
• references/proof-mode.md (N-null-hypothesis structure for finding verification)
• references/prompt-templates.md (advocate/skeptic templates enforcing anti-balance)
• references/synthesis.md (verdict table format + recommendation structure)
• references/anti-patterns.md (10 common failure modes with diagnoses)

When to use

• Choosing between competing technical approaches
• Verifying a bug finding is real (not a false positive)
• Reviewing a design decision before commit
• Any claim the caller is inclined to agree with by default

Test plan

• python3 .github/scripts/validate_codex_skills.py passes (verified locally)
• Plugin registered in .claude-plugin/marketplace.json
• CODEOWNERS entry added
• README table entry added under Verification section
• Codex symlink created at .codex/skills/adversarial-verification
• Install the plugin locally and invoke the skill on a real claim
• Verify both decision-mode and proof-mode paths produce useful verdicts

🤖 Generated with Claude Code

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[dguido]

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