Update README to reflect new features, verify install and model info

[mickeylorenzini]

Summary

The README is stale — it reflects the initial release but not the verification criteria system, domain criteria, eval harness, or the docs/tests infrastructure added since. Install instructions and compatible model/platform claims also need verification against current behavior.

What needs updating

1. Document new features

• Verification criteria system — domain-specific audit criteria (e.g., Implementation Plans) that harden loads and applies
• Domain criteria files — extensible criteria in tests/fixtures/ and the pattern for adding new domains
• Eval harness — tests/run-eval.md and the fixture-based evaluation system for testing harden itself
• Anti-pattern detection — harden now catches known failure modes (e.g., static-only audits)

2. Verify install instructions

• Confirm claude.ai ZIP upload path still works (Settings → Capabilities → Add Skills)
• Confirm Claude Code install path (.claude/skills/) is accurate
• Verify Codex CLI / Gemini CLI paths are correct or update
• Test that the skill activates after a fresh install via at least one method

3. Verify applicable models / platforms

• Confirm compatibility field in SKILL.md frontmatter is accurate (claude.ai, Claude Code, Codex CLI, Gemini CLI)
• Note any platform-specific limitations (e.g., web search availability)
• Verify graceful degradation claim (works without web search)

4. Reflect repo structure

• README should acknowledge docs/, tests/, and CONTRIBUTING.md exist — users landing on the repo should know where to look

Acceptance criteria

• README documents verification criteria, domain criteria, eval harness, and anti-pattern detection
• All install instructions tested or verified against current platform docs
• Compatible platforms/models list is accurate
• Repo structure (docs, tests, CONTRIBUTING.md) surfaced to users
• No broken links in README

Likely affected files

• README.md
• SKILL.md (compatibility field, if corrections needed)