Bug: langchain-anthropic file_tool callback never emits args["old_path"] but _handle_rename reads it -> KeyError on every rename

### Submission checklist - [x] This is a bug, not a usage question. - [x] I added a clear and descriptive title that summarizes this issue. - [x] I used the GitHub search to find a similar question and didn't find it. - [x] I am sure that this is a bug in LangChain rather than my code. - [x] The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package). - [x] This is not related to the langchain-community package. - [x] I posted a self-contained, minimal, reproducible example. A maintainer can copy it and run it AS IS. ### Package (Required) - [ ] langchain - [ ] langchain-openai - [x] langchain-anthropic - [ ] langchain-classic - [ ] langchain-core - [ ] langchain-model-profiles - [ ] langchain-tests - [ ] langchain-text-splitters - [ ] langchain-chroma - [ ] langchain-deepseek - [ ] langchain-exa - [ ] langchain-fireworks - [ ] langchain-groq - [ ] langchain-huggingface - [ ] langchain-mistralai - [ ] langchain-nomic - [ ] langchain-ollama - [ ] langchain-openrouter - [ ] langchain-perplexity - [ ] langchain-qdrant - [ ] langchain-xai - [ ] Other / not sure / general ### Related Issues / PRs _No response_ ### Reproduction Steps / Example Code (Python) ```python import tempfile from pathlib import Path from langchain_anthropic.middleware.anthropic_tools import ( StateClaudeTextEditorMiddleware, StateClaudeMemoryMiddleware, FilesystemClaudeTextEditorMiddleware, FilesystemClaudeMemoryMiddleware, ) # Site 1: state-backed text editor mw = StateClaudeTextEditorMiddleware() state = {mw.state_key: {"/some/old.txt": { "content": "hi", "created_at": "2026-01-01T00:00:00+00:00", "modified_at": "2026-01-01T00:00:00+00:00", }}} try: mw._handle_rename( {"path": "/some/old.txt", "new_path": "/some/new.txt"}, state, "tc-1" ) except KeyError as e: print("state textedit:", repr(e)) # Site 2: state-backed memory (same base class) mw = StateClaudeMemoryMiddleware() state = {mw.state_…