fix(knowledge): 修复内容文件读取时的编码和错误提示

- 为知识块添加和更新命令的读取内容文件函数添加了可选的inline flag参数
- 更新readUtf8TextFile以支持根据inline flag生成更友好的ENOENT错误提示
- 确保内容读取时使用严格的UTF-8编码解码方式
- 如果读取文件失败，提供文件路径和权限相关的详细错误信息
- 校验知识块内容长度时保持一致的错误处理逻辑

packages/commands/src/commands/knowledge/chunk-add.ts

@@ -121,7 +121,9 @@ export default defineCommand({
       field = parseFieldEntries(flags.field);
     } else {
       const content =
-        flags.contentFile !== undefined ? readUtf8TextFile(flags.contentFile) : flags.content;
+        flags.contentFile !== undefined
+          ? readUtf8TextFile(flags.contentFile, "--content")
+          : flags.content;
       if (typeof content === "string" && content.length > 6000) {
         throw new BailianError("Chunk content must be at most 6000 characters", ExitCode.USAGE);
       }

packages/commands/src/commands/knowledge/chunk-update.ts

@@ -122,7 +122,9 @@ export default defineCommand({
     // dry-run also reads the file and validates (rehearsal semantics); the read-back
     // request is only made outside dry-run and when no new content is given
     let content =
-      flags.contentFile !== undefined ? readUtf8TextFile(flags.contentFile) : flags.content;
+      flags.contentFile !== undefined
+        ? readUtf8TextFile(flags.contentFile, "--content")
+        : flags.content;
     if (content !== undefined && (content.length < 10 || content.length > 6000)) {
       throw new BailianError("Chunk content must be 10-6000 characters", ExitCode.USAGE);
     }

packages/commands/src/commands/knowledge/upload-support.ts

@@ -192,22 +192,33 @@ const DOCUMENT_EXTENSIONS = new Set([
 ]);
 
 /**
- * Read a UTF-8 plain-text file (--content-file for chunk add/update).
+ * Read a UTF-8 plain-text file.
  * Support is defined by content, not extension: any UTF-8 text is valid.
  * Strict decode failure → USAGE, with a hint pointing to the document upload
  * flow when the extension is a document format; file I/O failure → GENERAL + errno.
+ *
+ * @param inlineAlternativeFlag When provided, an ENOENT on a value that looks
+ *   like inline text (no path separator / no extension) appends a hint pointing
+ *   the user to this flag instead. Pass the inline-text flag name (e.g.
+ *   `"--content"`) only from commands that have a file-vs-inline choice.
  */
-export function readUtf8TextFile(filePath: string): string {
+export function readUtf8TextFile(filePath: string, inlineAlternativeFlag?: string): string {
   let fileBuffer: Buffer;
   try {
     fileBuffer = readFileSync(filePath);
   } catch (error) {
     const errno = (error as { code?: string }).code ?? "unknown";
-    throw new BailianError(
-      `Cannot read file: ${filePath}`,
-      ExitCode.GENERAL,
-      `File system error (${errno}) — check the path and permissions.`,
-    );
+    let hint = `File system error (${errno}) — check the path and permissions.`;
+    if (
+      inlineAlternativeFlag &&
+      errno === "ENOENT" &&
+      !extname(filePath) &&
+      !filePath.includes("/") &&
+      !filePath.includes("\\")
+    ) {
+      hint += ` If you meant to pass text content directly, use ${inlineAlternativeFlag} instead of --content-file.`;
+    }
+    throw new BailianError(`Cannot read file: ${filePath}`, ExitCode.GENERAL, hint);
   }
   try {
     return new TextDecoder("utf-8", { fatal: true }).decode(fileBuffer);