✨ feat(vscode): 工单挂原型插件，详情面板一键导入 Figma

- prototypeFile 走通 state → Issue → webview 全链路（gitea/youtrack 两个
  loader、两份 KNOWN_STATE_FIELDS、issue/patch、webview types），按 planFile
  同款当共享字段；路径校验换成 .json 版，允许绝对路径
- 详情面板「计划文件」下加「原型插件路径」行：双击开 manifest.json，
  行尾按钮「在 Figma 中导入并打开」；没挂插件时只显示空态
- src/figma/：把 manifest 写进 Figma 桌面版的 localFileExtensions 再拉起
  Figma。坑是 Figma 退出会用内存状态覆盖 settings.json，所以写之前先
  osascript 优雅退出并轮询等它真没了（10s 等不到就让用户手动关，不强杀）；
  写前备份 settings.json.bak-<时间戳>；已导入过就跳过写入直接打开；
  非 macOS 只把路径复制到剪贴板
- webhook 里 spec/plan 的 marker 同步改成表驱动，顺带认第三种 prototype
- 提示词：prototype.md 要求画完挂 marker；brainstorm-continue.md 新增
  {prototypeRef} 占位符，有原型插件时让续聊先读它别从零重画，没有时
  连同整段抹掉

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

vscode/src/youtrack/issueLoader.ts

@@ -75,6 +75,7 @@ function toIssue(baseUrl: string, it: YouTrackIssue): Issue {
     prototypeProfilePath: str(state.prototypeProfilePath),
     specFile: str(state.specFile),
     planFile: str(state.planFile),
+    prototypeFile: str(state.prototypeFile),
     prDiffFile: str(state.prDiffFile),
     pr: str(state.pr),
     branch: str(state.branch),

vscode/src/youtrack/stateComment.ts

@@ -20,7 +20,7 @@ import { addComment, listComments } from './api'
 export const STATE_MARKER = '<!--spx-state-->'
 
 /** Same field set as the Gitea state blob — kept independent to avoid coupling. */
-const KNOWN_STATE_FIELDS = ['column', 'sessionId', 'implementSessionId', 'reviewSessionId', 'testSessionId', 'prototypeSessionId', 'profilePath', 'brainstormProfilePath', 'testProfilePath', 'prototypeProfilePath', 'specFile', 'planFile', 'prDiffFile', 'pr', 'prMerged', 'prMergedAt', 'branch', 'worktreePath', 'implementStatus', 'color', 'autoReview', 'handoffAttachmentId', 'handoffFrom'] as const
+const KNOWN_STATE_FIELDS = ['column', 'sessionId', 'implementSessionId', 'reviewSessionId', 'testSessionId', 'prototypeSessionId', 'profilePath', 'brainstormProfilePath', 'testProfilePath', 'prototypeProfilePath', 'specFile', 'planFile', 'prototypeFile', 'prDiffFile', 'pr', 'prMerged', 'prMergedAt', 'branch', 'worktreePath', 'implementStatus', 'color', 'autoReview', 'handoffAttachmentId', 'handoffFrom'] as const
 
 /**
  * Parse a comment body into a state object, or null if it isn't a state