Schema-first JSON contracts everywhere — no regex on free text

Every phase has a JSON Schema; every model call uses structured JSON mode. The schemas turned out to be the codebase's most valuable asset — the Phase 5 also-considered structure (next-best catalysts with explicit rejection reasons) and the Phase 6 credibility enum are domain modeling that only comes out of painful iteration. If everything else were thrown out tomorrow, the prompts and the schemas would still port to whatever replaced them.