fix: verdict parsing, README claims, example consistency

Fixes from adversarial code-vs-plan review (3 rounds):
- Verdict format in prompts now matches parser (bare tokens)
- Missing verdict treated as parse failure, not approval
- README: softened backend swappability to "designed for extensibility"
- Example: replaced incorrect FK scenario with valid transaction bug
- Example: aligned fixes and round-2 summary with round-1 finding

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

README.md

@@ -32,10 +32,10 @@ This skill is a text instruction that any AI agent can interpret.
 It actively fixes issues based on reviewer feedback and resubmits
 for re-review. Up to 5 rounds until approved.
 
-**Universal foundation** — the skill relies on basic agent capabilities:
-run a command, read a file, edit a file. The reviewer is a swappable
-component: today Codex, tomorrow Gemini CLI, next week a local model.
-Switching backends = changing one launch command; prompts and workflow stay the same.
+**Designed for extensibility** — the skill relies on basic agent capabilities:
+run a command, read a file, edit a file. The prompts and review workflow
+are model-agnostic. Currently uses OpenAI Codex as the reviewer;
+adding other backends (Gemini, local models) is on the roadmap.
 
 ## How it works