Document Zustand store action naming conventions in dev docs

[coderabbitai]

Background

When implementing Zustand store actions, we follow these naming conventions:

• Use setX for actions that simply change the value of a state
• Use updateX for actions that do more than simply changing a value (e.g., perform additional logic, make API calls, update multiple states)

Task

Add this naming convention to the development documentation to ensure consistent implementation across the codebase.

Example

// Example of a simple setter (use 'set' prefix)
setPageNum: (newPageNum: number) => {
  set({pageNum: newPageNum});
}

// Example of a complex action (use 'update' prefix)
updateIsPrettified: (newIsPrettified: boolean) => {
  // Has additional logic beyond just setting the value
  if (newIsPrettified === get().isPrettified) {
    return;
  }
  set({isPrettified: newIsPrettified});
  
  // Performs other actions...
  setUiState(UI_STATE.FAST_LOADING);
  // ...
}

References

Related PR: #286