\eqref displays ??? when \label and \tag is defined in another cell

To replicate:

Cell 1 has
```
$$a = 1 \label{eq:1}\tag{1}$$
See $\eqref{eq:1}$
```

Cell 2 has
```
See $\eqref{eq:1}$
```

Cell 2 displays `See ???` instead of See (1).

Reproduce the issue by creating the two cells shown and checking how the equation label is rendered across cells. Trace the notebook's math rendering and label-resolution path; done means Cell 2 displays `See (1)` instead of `See ???`.

Written by the indexing model from the issue text.