fix: keep node file content byte-faithful in node_file_get

Splitting the file with keepends=False and rejoining with newlines
dropped the trailing newline of the last line (and every \r of CRLF
files), so returned content was shorter than the file on disk and did
not round-trip. Split with keepends=True and join the selected lines
verbatim; pagination semantics are unchanged.

gns3server/agent/gns3_copilot/gns3_client/api_handlers.py

@@ -474,23 +474,26 @@ def get_node_file_handler(params: dict[str, Any], gns3_ctx: dict[str, Any]) -> d
         raw = raw[:MAX_NODE_FILE_BYTES]
         truncated = True
 
-    lines = raw.splitlines(keepends=False)
+    # keepends keeps the content byte-faithful: the trailing newline of the
+    # last line and any \r\n endings survive the round trip
+    lines = raw.splitlines(keepends=True)
     total_lines = len(lines)
 
     # Apply offset/limit
     selected = lines[offset: offset + limit] if offset < total_lines else []
     has_more = (offset + limit) < total_lines or truncated
+    content = "".join(selected)
 
     return {
         "file_path": file_path,
-        "content": "\n".join(selected),
+        "content": content,
         "metadata": {
             "total_lines": total_lines,
             "total_bytes": total_bytes,
             "offset": offset,
             "limit": limit,
             "returned_lines": len(selected),
-            "returned_bytes": len("\n".join(selected).encode("utf-8")),
+            "returned_bytes": len(content.encode("utf-8")),
             "truncated": truncated or has_more,
             "has_more": has_more,
         },