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

@@ -23,6 +23,7 @@ interface SubmitValues {
   reviewPrompt: string
   devBranch: string
   autoBuildBranch: string
+  worktreeDirectory: string
   worktreePostCreateScript: string
   worktreePreRemoveScript: string
   implTabPreCreateScript: string
@@ -59,6 +60,7 @@ export interface SettingsModalProps {
   initialReviewPrompt: string
   initialDevBranch: string
   initialAutoBuildBranch: string
+  initialWorktreeDirectory: string
   initialWorktreePostCreateScript: string
   initialWorktreePreRemoveScript: string
   initialImplTabPreCreateScript: string
@@ -128,6 +130,7 @@ export function SettingsModal({
   initialReviewPrompt,
   initialDevBranch,
   initialAutoBuildBranch,
+  initialWorktreeDirectory,
   initialWorktreePostCreateScript,
   initialWorktreePreRemoveScript,
   initialImplTabPreCreateScript,
@@ -151,6 +154,7 @@ export function SettingsModal({
   const [reviewPrompt, setReviewPrompt] = useState(initialReviewPrompt)
   const [devBranch, setDevBranch] = useState(initialDevBranch)
   const [autoBuildBranch, setAutoBuildBranch] = useState(initialAutoBuildBranch)
+  const [worktreeDirectory, setWorktreeDirectory] = useState(initialWorktreeDirectory)
   const [worktreePostCreateScript, setWorktreePostCreateScript] = useState(initialWorktreePostCreateScript)
   const [worktreePreRemoveScript, setWorktreePreRemoveScript] = useState(initialWorktreePreRemoveScript)
   const [implTabPreCreateScript, setImplTabPreCreateScript] = useState(initialImplTabPreCreateScript)
@@ -252,6 +256,8 @@ export function SettingsModal({
       reviewPrompt,
       devBranch: devBranch.trim(),
       autoBuildBranch: autoBuildBranch.trim(),
+      // worktree 目录模板：trim 后留空 = 用默认模板（getSettings 读时回退）
+      worktreeDirectory: worktreeDirectory.trim(),
       // 钩子路径保持原样 trim（前后空格无意义；空串 = 用默认 .spx/*.sh）
       worktreePostCreateScript: worktreePostCreateScript.trim(),
       worktreePreRemoveScript: worktreePreRemoveScript.trim(),
@@ -605,6 +611,37 @@ export function SettingsModal({
 
             {activeGroup === 'hooks' && (
               <>
+                <Field
+                  label="工作树目录"
+                  hint={(
+                    <>
+                      实施 Plan 时创建 worktree 的目录模板。占位符
+                      {' '}
+                      <code>$project_root</code>
+                      （工作区绝对路径）、
+                      <code>$project_name</code>
+                      （工作区目录名）、
+                      <code>$feature_name</code>
+                      （spec/plan 的 slug）；开头
+                      {' '}
+                      <code>~</code>
+                      {' '}
+                      展开为主目录。留空 = 默认
+                      {' '}
+                      <code>~/Sources/worktree/$project_name/$feature_name</code>
+                      。
+                    </>
+                  )}
+                >
+                  <input
+                    type="text"
+                    value={worktreeDirectory}
+                    onChange={e => setWorktreeDirectory(e.target.value)}
+                    placeholder="~/Sources/worktree/$project_name/$feature_name"
+                    className={inputClass}
+                  />
+                </Field>
+
                 <Field
                   label="worktree 创建后脚本"
                   hint={(