♻️ refactor(vscode): 续聊里的原型段落搬进模板文件

那段正文原先拼在 prompts.ts 里，设置面板看不到也改不了。现在落到
prompts/brainstorm-continue-prototype.md，面板「提示词」组多一项「续聊·原型段落」，
占位符 {prototypeFile} / {issueNumber} / {prototypeSessionId}；取值为空的整行会被
删掉，免得留下半句没有值的说明。

同时把措辞收紧：原型改动只能 ListAgents + SendMessage 给已开着的原型会话，
点名禁止派子代理 / fork 分身 / 自己动插件代码。

Claude-Session: https://claude.ai/code/session_01Kgmb1LvrPmFX3NoUDB4zZC

vscode/webview-ui/src/components/SettingsModal.tsx

@@ -22,6 +22,7 @@ interface SubmitValues {
   webhookSecret: string
   brainstormPrompt: string
   brainstormContinuePrompt: string
+  prototypeRefPrompt: string
   implementPlanPrompt: string
   autoReview: boolean
   reviewPrompt: string
@@ -78,6 +79,7 @@ export interface SettingsModalProps {
   initialWebhookSecret: string
   initialBrainstormPrompt: string
   initialBrainstormContinuePrompt: string
+  initialPrototypeRefPrompt: string
   initialImplementPlanPrompt: string
   initialAutoReview: boolean
   initialReviewPrompt: string
@@ -170,6 +172,7 @@ export function SettingsModal({
   initialWebhookSecret,
   initialBrainstormPrompt,
   initialBrainstormContinuePrompt,
+  initialPrototypeRefPrompt,
   initialImplementPlanPrompt,
   initialAutoReview,
   initialReviewPrompt,
@@ -214,6 +217,7 @@ export function SettingsModal({
   const [webhookSecret, setWebhookSecret] = useState(initialWebhookSecret)
   const [brainstormPrompt, setBrainstormPrompt] = useState(initialBrainstormPrompt)
   const [brainstormContinuePrompt, setBrainstormContinuePrompt] = useState(initialBrainstormContinuePrompt)
+  const [prototypeRefPrompt, setPrototypeRefPrompt] = useState(initialPrototypeRefPrompt)
   const [implementPlanPrompt, setImplementPlanPrompt] = useState(initialImplementPlanPrompt)
   const [autoReview, setAutoReview] = useState(initialAutoReview)
   const [reviewPrompt, setReviewPrompt] = useState(initialReviewPrompt)
@@ -260,6 +264,7 @@ export function SettingsModal({
     setWebhookSecret(initialWebhookSecret)
     setBrainstormPrompt(initialBrainstormPrompt)
     setBrainstormContinuePrompt(initialBrainstormContinuePrompt)
+    setPrototypeRefPrompt(initialPrototypeRefPrompt)
     setImplementPlanPrompt(initialImplementPlanPrompt)
     setAutoReview(initialAutoReview)
     setReviewPrompt(initialReviewPrompt)
@@ -354,6 +359,7 @@ export function SettingsModal({
       webhookSecret: webhookSecret.trim(),
       brainstormPrompt,
       brainstormContinuePrompt,
+      prototypeRefPrompt,
       implementPlanPrompt,
       autoReview,
       reviewPrompt,
@@ -1010,6 +1016,30 @@ export function SettingsModal({
                   />
                 </Field>
 
+                <Field
+                  label="续聊·原型段落"
+                  hint={(
+                    <>
+                      工单挂了原型插件时，这段会填进续聊提示词的
+                      <code>{'{prototypeRef}'}</code>
+                      处。可用占位符：
+                      <code>{'{prototypeFile}'}</code>
+                      、
+                      <code>{'{issueNumber}'}</code>
+                      、
+                      <code>{'{prototypeSessionId}'}</code>
+                      （取值为空时，含该占位符的整行会被删掉）
+                    </>
+                  )}
+                >
+                  <textarea
+                    rows={8}
+                    value={prototypeRefPrompt}
+                    onChange={e => setPrototypeRefPrompt(e.target.value)}
+                    className={`${inputClass} resize-y font-mono`}
+                  />
+                </Field>
+
                 <Field
                   label="实施提示词"
                   hint={(