feat(kol): add selection-based AI optimize for prompt editor

Trigger an AI optimize panel from a text selection in the KOL prompt
editor, accept a user instruction, and stream a preview before replacing
the selected fragment. Extend the shared editor AI assist panel with
boundary-aware placement so it can be hosted inside scoped surfaces, and
update the backend optimize prompt to honor the user instruction.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/admin-web/src/i18n/messages/en-US.ts

@@ -274,7 +274,10 @@ const enUS = {
         preview: "Preview form",
         aiGenerate: "AI Generate",
         aiOptimize: "AI Optimize",
-        aiPlaceholder: "Describe the prompt effect you want, and AI will generate or optimize it...",
+        aiPlaceholder: "Describe the prompt effect you want, and AI will generate it...",
+        aiOptimizePromptPlaceholder: "For example: make this prompt clearer, keep variable placeholders, and reduce ambiguity.",
+        aiOptimizeDisclaimer: "AI output is for reference only. Review it before replacing the selected prompt text.",
+        aiOptimizeReplace: "Replace selection",
       },
       variable: {
         input: "Input",

apps/admin-web/src/i18n/messages/zh-CN.ts

@@ -274,7 +274,10 @@ const zhCN = {
         preview: "预览表单",
         aiGenerate: "AI 生成",
         aiOptimize: "AI 优化",
-        aiPlaceholder: "描述你想要的 prompt 效果，AI 帮你生成 / 优化...",
+        aiPlaceholder: "描述你想要的 prompt 效果，AI 帮你生成...",
+        aiOptimizePromptPlaceholder: "例如：让这段提示词更清晰，保留变量占位符，减少歧义。",
+        aiOptimizeDisclaimer: "AI 生成内容仅供参考，请确认后再替换选中片段。",
+        aiOptimizeReplace: "替换选中内容",
       },
       variable: {
         input: "输入框",