<think>
Okay, I need to implement the cell_name and grid_cells functions. Let's start with cell_name. The problem says that row and column are zero-based, but the output should be a column letter (A, B, etc.) followed by a row number starting from 1. 

First, the column part. For example, column 0 is 'A', 1 is 'B', up to 25 is 'Z'. But if the column is 26, that's beyond the 26th letter. Wait, the problem says that if the column is beyond the 26th, how to name it? The task says that the column beyond the 26th is not stated. Oh, right, the user mentioned that this is a blocked point. But the problem says to implement it. Hmm. Wait, the user's instruction says that the task is to implement cell_name and grid_cells. But the problem says that the column beyond the 26th is not stated. So how to handle that?

Wait, the problem says that the column is counted from zero. So for example, column 0 is A, 1 is B, ..., 25 is Z. Then, column 26 would be AA, right? Because in Excel, columns go A, B, ..., Z, then AA, AB, etc. So the function needs to convert the column number to the appropriate letters. So for column numbers beyond 26, we need to compute the letters accordingly.

So, how to convert a zero-based column number to the spreadsheet column letters. Let's think. For example, column 0 is A (1 in 1-based), column 25 is Z (26 in 1-based). Then column 26 would be AA (since 26 is 26 in 1-based, which is 26 letters, but since each letter is 26, so 26 is 26 in 1-based, which is Z, but then 26+1 is 27, which would be AA. Wait, maybe the conversion is similar to converting a number to a base-26 system, but with letters A-Z, and with 0-based index. Wait, but in Excel, the column letters are like A=1, B=2, ..., Z=26, then AA=27, AB=28, etc. So the column number is 1-based. But in our case, the input is zero-based. So for example, if the column is 0, that's A (1-based 1). So the function needs to convert the column number (zero-based) to the corresponding letters.

So the approach is to take the column number, add 1 to make it 1-based, then convert that to the letters. For example, column 0 becomes 1, which is A. Column 25 becomes 26, which is Z. Column 26 becomes 27, which is AA.

So the problem is to convert a number (column) to the corresponding letters. How to do that? Let's think of it as a base-26 conversion, but with the letters A-Z, and each digit is 0-25. But since in base 26, each digit is 0-25, but in this case, the letters are A-Z, which correspond to 0-25. Wait, but in the case of 26, the number would be 26, which is 26 in base 26, which would be 'Z' (since 26 is 26 in base 26, which