Formatting uses snprintf into an internal 256-byte buffer, including the
terminator. Get returns the format pointer, not the rendered buffer.
Construction permits NULL for no text. DupInfoText decides whether the
format is borrowed or copied. With borrowing, keep it valid until
replacement or disposal; do not modify it in place to request an update.
Setting compares string contents. Equal text becomes TAG_IGNORE and
retains the old pointer, even if a different pointer was supplied.
Replacing an existing non-NULL string with NULL reaches strcmp with NULL
and is unsafe. An empty string can display no characters but still
counts as a present InfoText for sizing.
A changed string is formatted with the post-division Current and
requests redraw, but no size remeasurement. Copy failure leaves InfoText
NULL without reporting setter failure. In copy mode the old string is
freed before duplication; a replacement must not point inside that owned
allocation. Current and Divide changes also reformat; Max alone does
not.