Replace MMKV with C file writing

[stevenconner]

What does this PR do?

• Replaces MMKV-backed storage with a small C file-writing implementation for macOS.
• Simplifies native dependencies and reduces build flakiness related to MMKV.
• Persists timeline logs and preferences using the new file-based approach.
• Includes migration and cleanup to remove MMKV usage.

What GitHub issues does this PR fix?

• Resolves Replace mmkv with C++ file writing #38.

How to verify this code works?

reactotron-macos setup for this PR

1. gh pr checkout 57
2. npm install
3. npm run pod
4. npm run start
5. npm run macos

Step by step of how to test this PR

1. Launch reactotron-macos from this branch and start the example app.
2. Ensure the app connects to the standalone server on port 9292 and logs appear.
3. Trigger state changes and network requests; confirm timeline entries are recorded.
4. Quit and relaunch reactotron-macos; verify prior timeline entries persist (new file storage).
5. Confirm there are no references to MMKV in build logs or runtime.
6. Check Console for absence of new warnings/errors related to storage.

Windows

This is not tested on windows...

[joshuayoes]

request: remove react-native-mmkv from the package.json and update the lock files

reactotron-macos/package.json

Line 29 in 7263835

"react-native-mmkv": "^3.3.0",

[joshuayoes]

Things seem to be looking pretty good. I tried quitting and reload and it seemed to retrieve some info from reloading. It didn't persist the logs but I'm not sure that is necessary.

Replace-MMKV-with-C-file.mov

I am noticing that even without the temp file, it seems to be persisting some client info when I quit and reload?

Screen.Recording.2025-10-10.at.3.08.32.PM.mov

[joshuayoes]

nit: on windows, this would be better put temp in C:\Users\Username\AppData\Local\Temp. But for now this is okay.

[frankcalise]

You should be able to utilize std::filesystem::path temp = std::filesystem::temp_directory_path(); That'll get the path Josh is talking about (and also should be good on macOS also)

https://en.cppreference.com/w/cpp/filesystem/temp_directory_path.html