feat(skill): add skill file browsing capability

- Add API endpoints for listing/reading/writing skill files
- Add FileTree component in SkillForm for directory browsing
- Users can now view scripts/, references/, assets/ directories
- Files can be selected and edited in the instructions textarea
- Add translations for new file browsing features

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/src/i18n/locales/en-US.ts

@@ -1404,6 +1404,13 @@ const enUS = {
     selectFromSidebar: 'Select a skill from the sidebar',
     dangerZone: 'Danger Zone',
     dangerZoneDescription: 'Irreversible and destructive actions',
+    files: 'Files',
+    noFiles: 'No files found',
+    loadFilesError: 'Failed to load files: ',
+    readFileError: 'Failed to read file: ',
+    saveFile: 'Save File',
+    saveFileSuccess: 'File saved successfully',
+    saveFileError: 'Failed to save file: ',
   },
   wizard: {
     sidebarDescription: 'Create a bot with guided steps',

web/src/i18n/locales/zh-Hans.ts

@@ -1347,6 +1347,13 @@ const zhHans = {
     selectFromSidebar: '从侧边栏选择一个技能',
     dangerZone: '危险区域',
     dangerZoneDescription: '不可逆的操作',
+    files: '文件',
+    noFiles: '暂无文件',
+    loadFilesError: '加载文件失败：',
+    readFileError: '读取文件失败：',
+    saveFile: '保存文件',
+    saveFileSuccess: '文件保存成功',
+    saveFileError: '保存文件失败：',
   },
   wizard: {
     sidebarDescription: '通过引导步骤创建机器人',