Fix the re-render counter for a Zustand port

An AI agent moved your React app's state from Redux to Zustand. The data is the same, but you want to check that components re-render as often as before. You model the store and count the re-renders a list of writes causes.

An assistant wrote count_rerenders(subscriptions, updates). It is in the editor. It has a bug. Find it and fix it.

Input and output:

• subscriptions: one string per component, "Name:fields". The fields are * for the whole store, or field names joined by |.
• updates: the store writes in order, each "field=value".
• Return one re-render count per subscription, in the same order.

Rules the tests check:

• Split a subscription at its first :. With no :, the component reads nothing. The name is ignored.
• Trim the part after the :. If it is exactly *, the component reads the whole store. Otherwise split it on |, trim each field name and drop empty ones.
• Split an update at its first = and trim both sides. Skip an update with no = or with an empty field name.
• The store starts empty. An update is a change when its field has never been written, or when the field's current value differs from the new value.
• An update that writes the value its field already holds changes nothing, and nobody re-renders.
• On a change, every whole-store component re-renders once. Any other component re-renders once if it reads that field, even when it lists the field twice.