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/openai-to-kiro.js

@@ -270,6 +270,7 @@ function convertMessages(messages, tools, model) {
     let role = msg.role;
 
     // Normalize: system/tool -> user
+    const wasSystem = role === ROLE.SYSTEM;
     if (role === ROLE.SYSTEM || role === ROLE.TOOL) {
       role = ROLE.USER;
     }
@@ -338,7 +339,10 @@ function convertMessages(messages, tools, model) {
           content: [{ text: toolContent }]
         });
       } else if (content) {
-        pendingUserContent.push(content);
+        // <instructions> tags: Claude models treat these as authoritative directives.
+        pendingUserContent.push(
+          wasSystem ? `<instructions>\n${content}\n</instructions>` : content
+        );
       }
     } else if (role === ROLE.ASSISTANT) {
       // Extract text content and tool uses