Revert "feat: 添加 GBK 编码自动检测支持，文件读写工具透明处理非 UTF-8 文件"

This reverts commit 0ce8f7a1cb.

src/utils/fileRead.ts

@@ -13,24 +13,39 @@
  */
 
 import { logForDebugging } from './debug.js'
-import { type FileEncoding, decodeBuffer, detectEncoding } from './encoding.js'
 import { getFsImplementation, safeResolvePath } from './fsOperations.js'
 
 export type LineEndingType = 'CRLF' | 'LF'
 
 export function detectEncodingForResolvedPath(
   resolvedPath: string,
-): FileEncoding {
+): BufferEncoding {
   const { buffer, bytesRead } = getFsImplementation().readSync(resolvedPath, {
     length: 4096,
   })
 
-  // Empty files default to utf8 — nothing to detect
+  // Empty files should default to utf8, not ascii
+  // This fixes a bug where writing emojis/CJK to empty files caused corruption
   if (bytesRead === 0) {
     return 'utf8'
   }
 
-  return detectEncoding(buffer.subarray(0, bytesRead))
+  if (bytesRead >= 2) {
+    if (buffer[0] === 0xff && buffer[1] === 0xfe) return 'utf16le'
+  }
+
+  if (
+    bytesRead >= 3 &&
+    buffer[0] === 0xef &&
+    buffer[1] === 0xbb &&
+    buffer[2] === 0xbf
+  ) {
+    return 'utf8'
+  }
+
+  // For non-empty files, default to utf8 since it's a superset of ascii
+  // and handles all Unicode characters properly
+  return 'utf8'
 }
 
 export function detectLineEndingsForString(content: string): LineEndingType {
@@ -59,7 +74,7 @@ export function detectLineEndingsForString(content: string): LineEndingType {
  */
 export function readFileSyncWithMetadata(filePath: string): {
   content: string
-  encoding: FileEncoding
+  encoding: BufferEncoding
   lineEndings: LineEndingType
 } {
   const fs = getFsImplementation()
@@ -70,10 +85,10 @@ export function readFileSyncWithMetadata(filePath: string): {
   }
 
   const encoding = detectEncodingForResolvedPath(resolvedPath)
-  // Read raw Buffer first — readFileSync encoding option only accepts
-  // BufferEncoding, not gbk etc.
-  const rawBuffer = fs.readFileBytesSync(resolvedPath)
-  const raw = decodeBuffer(rawBuffer, encoding)
+  const raw = fs.readFileSync(resolvedPath, { encoding })
+  // Detect line endings from the raw head before CRLF normalization erases
+  // the distinction. 4096 code units is ≥ detectLineEndings's 4096-byte
+  // readSync sample (line endings are ASCII, so the unit mismatch is moot).
   const lineEndings = detectLineEndingsForString(raw.slice(0, 4096))
   return {
     content: raw.replaceAll('\r\n', '\n'),