✨ feat(vscode): 新增第五种工单会话「原型会话」

照测试会话那条链路补一份 prototype：

- 消息与路由：session/start-prototype、session/resume-prototype、
  issue/update-prototype-profile-path，都进只读门禁
- 会话：handleStartPrototypeSession / handleResumePrototypeSession，
  终端名 issue-N-原型；cwd 有 worktree 用 worktree、没有退主仓库根
  （原 resolveTestSessionCwd 改名 resolveWorktreeOrRootCwd 两种会话共用）
- 不要求有 PR，任何阶段都能起；前置工单锁仍然拦
- 提示词：新增 prompts/prototype.md，设置里可改，占位符 {issueNumber}
- profile：工单级 prototypeProfilePath > 设置里的原型默认 profile >
  内置默认，与其它会话互不回退
- 状态字段 prototypeSessionId / prototypeProfilePath / prototypeTabOpen
  贯通 gitea、youtrack、本机 state 与移交包
- 详情面板加「原型会话id」「原型配置文件」两行，设置面板加对应两项

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

vscode/src/cc/handoffManifest.ts

@@ -1,15 +1,17 @@
-export type ClaudeSessionKind = 'brainstorm' | 'implement' | 'test'
+export type ClaudeSessionKind = 'brainstorm' | 'implement' | 'test' | 'prototype'
 
 export const CLAUDE_SESSION_FIELDS = [
   { field: 'sessionId', kind: 'brainstorm' },
   { field: 'implementSessionId', kind: 'implement' },
   { field: 'testSessionId', kind: 'test' },
-] as const satisfies ReadonlyArray<{ field: 'sessionId' | 'implementSessionId' | 'testSessionId', kind: ClaudeSessionKind }>
+  { field: 'prototypeSessionId', kind: 'prototype' },
+] as const satisfies ReadonlyArray<{ field: 'sessionId' | 'implementSessionId' | 'testSessionId' | 'prototypeSessionId', kind: ClaudeSessionKind }>
 
 export interface HandoffSessions {
   sessionId?: string
   implementSessionId?: string
   testSessionId?: string
+  prototypeSessionId?: string
   reviewSessionId?: string
 }
 
@@ -17,6 +19,7 @@ export interface HandoffProfiles {
   profilePath?: string
   brainstormProfilePath?: string
   testProfilePath?: string
+  prototypeProfilePath?: string
 }
 
 export interface HandoffManifest {
@@ -38,7 +41,7 @@ export function handoffAttachmentName(issueNumber: number): string {
   return `spx-handoff-issue-${issueNumber}.tgz`
 }
 
-const KINDS: ReadonlySet<string> = new Set<ClaudeSessionKind>(['brainstorm', 'implement', 'test'])
+const KINDS: ReadonlySet<string> = new Set<ClaudeSessionKind>(['brainstorm', 'implement', 'test', 'prototype'])
 
 // Claude / Codex 会话 id 都是 UUID；顺手挡掉路径穿越（如 `../x`）之类的伪造条目。
 const UUID_RE = /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i
@@ -80,13 +83,13 @@ export function parseHandoffManifest(json: string, expectedIssue: number): Hando
     return { id, relPath }
   })
   const sessions: HandoffSessions = {}
-  for (const k of ['sessionId', 'implementSessionId', 'testSessionId', 'reviewSessionId'] as const) {
+  for (const k of ['sessionId', 'implementSessionId', 'testSessionId', 'prototypeSessionId', 'reviewSessionId'] as const) {
     const v = optString(sessionsRaw[k])
     if (v)
       sessions[k] = v
   }
   const profiles: HandoffProfiles = {}
-  for (const k of ['profilePath', 'brainstormProfilePath', 'testProfilePath'] as const) {
+  for (const k of ['profilePath', 'brainstormProfilePath', 'testProfilePath', 'prototypeProfilePath'] as const) {
     const v = optString(profilesRaw[k])
     if (v)
       profiles[k] = v