✨ feat(vscode): 文件和文件夹在预览顶部问

侧栏「问 AI」打开代码阅读预览。文件夹是没有代码块的一页，源码文件在整页顶部聊，代码块下面的问答不动。历史按工作区文件夹和相对路径记在窗口状态里，不写进按块存的记录。

vscode/src/codeReader/qa/pathAskDescribe.ts

@@ -0,0 +1,35 @@
+/**
+ * 顶部问答带给模型的材料：文件是相对路径加开头若干行，文件夹是相对路径加这一层的名字。
+ */
+
+import type { Uri, WorkspaceFolder } from 'vscode'
+import type { ExcludeSetting } from '../explorer/fileEntries'
+import type { PathAskSubject, PathChild } from './pathAskPrompt'
+import { FileType, workspace } from 'vscode'
+import { createExcludeMatcher, sortEntries } from '../explorer/fileEntries'
+import { readFileHead } from './pathAskContext'
+import { displayRelativePath } from './pathQa'
+
+export async function describePath(target: { uri: Uri, folder: WorkspaceFolder, isDirectory: boolean, relativePath: string }): Promise<PathAskSubject> {
+  const relativePath = displayRelativePath(target.relativePath)
+  if (target.isDirectory)
+    return { kind: 'folder', relativePath, children: await folderChildren(target.uri, target.folder, target.relativePath) }
+  return { kind: 'file', relativePath, head: await readFileHead(target.uri.fsPath) }
+}
+
+/** 文件夹这一层的子文件和子目录；files.exclude 排除的不列。列不出来时只留原因。 */
+async function folderChildren(uri: Uri, folder: WorkspaceFolder, relativePath: string): Promise<PathChild[] | { unavailable: string }> {
+  let entries: [string, FileType][]
+  try {
+    entries = await workspace.fs.readDirectory(uri)
+  }
+  catch (err) {
+    const message = err instanceof Error ? err.message : String(err)
+    return { unavailable: `列不出来（${message}）。` }
+  }
+  const excluded = createExcludeMatcher(workspace.getConfiguration('files', folder).get<ExcludeSetting>('exclude'))
+  const names = new Set(entries.map(([name]) => name))
+  return sortEntries(entries.map(([name, type]) => ({ name, isDirectory: (type & FileType.Directory) !== 0 })))
+    .filter(entry => !excluded(relativePath ? `${relativePath}/${entry.name}` : entry.name, names))
+    .map(entry => ({ name: entry.name, kind: entry.isDirectory ? 'folder' : 'file' }))
+}