langchain-profiles refresh corrupts strings containing JSON literal substrings

### 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 - [ ] langchain-anthropic - [ ] langchain-classic - [ ] langchain-core - [x] 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 I searched open and closed issues and pull requests for the serializer expression, `langchain-profiles refresh`, JSON literal replacement, and model-profile string corruption. I found no pre-existing report or implementation. #39737 was my earlier submission and was automatically closed only because it was created programmatically instead of through this required web form; this web-form report is the canonical one. Open PR #39605 touches the same CLI for unrelated stale-augmentation validation but leaves this serializer unchanged. ### Reproduction Steps / Example Code (Python) ```python import runpy from pathlib import Path from tempfile import TemporaryDirectory from unittest.mock import Mock, patch from langchain_model_profiles.cli import refresh payload = { "anthropic": { "id": "anthropic", "name": "A…