fix(kiro): deliver system prompt natively, add Opus 4.5/4.7/4.8, tolerate dash version ids (#2366)

- 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>

open-sse/translator/request/claude-to-openai.js

@@ -129,14 +129,15 @@ function fixMissingToolResponsesOpenAI(messages) {
   }
 }
 
-// Wrap mid-conversation system text so it ends as a user turn (avoids Anthropic prefill 400)
+// Wrap mid-conversation system text so it ends as a user turn (avoids Anthropic prefill 400).
+// Uses <instructions> tags that Claude models treat as authoritative directives.
 function systemReminderText(content) {
   const parts = Array.isArray(content)
     ? content.filter(c => c?.type === CLAUDE_BLOCK.TEXT).map(c => c.text || "")
     : [typeof content === "string" ? content : ""];
   const text = parts.filter(Boolean).join("\n");
   if (!text.trim()) return "";
-  return `<system-reminder>\n${text}\n</system-reminder>`;
+  return `<instructions>\n${text}\n</instructions>`;
 }
 
 // Convert single Claude message - returns single message or array of messages