- Pass system prompt via native systemInstruction field (+ <instructions> fallback)
so Claude models stop treating it as info-only <system-reminder>
- Add Opus 4.5/4.7/4.8 (base/thinking/agentic/thinking+agentic) to Kiro registry
- normalizeModelId(): dash->dot version separator, scoped to Kiro provider only
- Replace <system-reminder> with <instructions> in claude-to-openai/openai-to-kiro
Co-authored-by: Cursor <cursoragent@cursor.com>