🔧 fix(vscode): worktree 目录配置改用插件自带设置面板，撤销 VS Code 原生配置

上一版误把 worktree 目录模板注册成 VS Code 原生设置（contributes.configuration
+ workspace.getConfiguration），但本插件有自己的设置面板（SettingsModal，存 globalState）。
改为：
- Settings 新增 worktreeDirectory 字段（默认 ~/Sources/worktree/$project_name/$feature_name，
  留空回退默认），贯穿 store/handler/两端 messages/useIssues/App/SettingsModal
- SettingsModal「钩子」分组新增「工作树目录」输入项，走既有 save/load 流程
- handleImplement 改从 getSettings(panel.context).worktreeDirectory 读模板
- 删除 package.json 的 contributes.configuration（meta.ts 为 gitignore 生成物，已本地还原）

deriveSlug / resolveWorktreeDir / ~ 展开 / 绝对路径 / feature/<slug> 逻辑不变。

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

vscode/src/panel/handlers/settings.ts

@@ -25,6 +25,7 @@ export async function handleSettingsSave(panel: KanbanWebviewPanel, payload: {
   reviewPrompt: string
   devBranch: string
   autoBuildBranch: string
+  worktreeDirectory: string
   worktreePostCreateScript: string
   worktreePreRemoveScript: string
   implTabPreCreateScript: string
@@ -43,6 +44,9 @@ export async function handleSettingsSave(panel: KanbanWebviewPanel, payload: {
   const trimmedYtToken = payload.youtrackToken.trim()
   const trimmedDevBranch = payload.devBranch.trim()
   const trimmedAutoBuildBranch = payload.autoBuildBranch.trim()
+  // worktree dir template: '' = "use default", so don't preserve blanks
+  // specially — getSettings falls back to the default at read time.
+  const trimmedWorktreeDir = payload.worktreeDirectory.trim()
   // Hook script paths: keep '' meaningful (= "use default
   // .spx/*.sh"). Just strip whitespace.
   const trimmedPostCreate = payload.worktreePostCreateScript.trim()
@@ -71,6 +75,7 @@ export async function handleSettingsSave(panel: KanbanWebviewPanel, payload: {
       reviewPrompt: payload.reviewPrompt || prev.reviewPrompt,
       devBranch: trimmedDevBranch || prev.devBranch,
       autoBuildBranch: trimmedAutoBuildBranch,
+      worktreeDirectory: trimmedWorktreeDir || prev.worktreeDirectory,
       worktreePostCreateScript: trimmedPostCreate,
       worktreePreRemoveScript: trimmedPreRemove,
       implTabPreCreateScript: trimmedImplPre,
@@ -89,6 +94,7 @@ export async function handleSettingsSave(panel: KanbanWebviewPanel, payload: {
     // fallback at read time.
     devBranch: trimmedDevBranch,
     autoBuildBranch: trimmedAutoBuildBranch,
+    worktreeDirectory: trimmedWorktreeDir,
     worktreePostCreateScript: trimmedPostCreate,
     worktreePreRemoveScript: trimmedPreRemove,
     implTabPreCreateScript: trimmedImplPre,
@@ -168,6 +174,7 @@ export async function handleEditSettingsRequest(panel: KanbanWebviewPanel): Prom
     reviewPrompt: s.reviewPrompt,
     devBranch: s.devBranch,
     autoBuildBranch: s.autoBuildBranch,
+    worktreeDirectory: s.worktreeDirectory,
     worktreePostCreateScript: s.worktreePostCreateScript,
     worktreePreRemoveScript: s.worktreePreRemoveScript,
     implTabPreCreateScript: s.implTabPreCreateScript,