feat: file viewer added

webui/backend/app/fs/filesystem_adapter.py

@@ -59,3 +59,17 @@ class FilesystemAdapter:
                 if on_progress:
                     on_progress(out_f.tell())
         shutil.copystat(src, dst, follow_symlinks=False)
+
+    def read_text_preview(self, path: Path, max_bytes: int, encoding: str = "utf-8") -> dict:
+        size = int(path.stat().st_size)
+        limit = max_bytes + 1
+        with path.open("rb") as in_f:
+            raw = in_f.read(limit)
+        truncated = size > max_bytes or len(raw) > max_bytes
+        if truncated:
+            raw = raw[:max_bytes]
+        return {
+            "size": size,
+            "truncated": truncated,
+            "content": raw.decode(encoding, errors="replace"),
+        }