controls/SelectionModel.qml kept the anchor in a string property and then
looked it up with a strict comparison, so a list whose rows carry numeric
ids never found its anchor again and every Shift-click there degraded to a
plain toggle. Ids now compare as strings, which is what the selection map
keys already were.
The range fill also wrote `m[rows[i].id]` for every row in the span, so a
list that mixes group headers into its rows gained an "undefined" key and a
count one above the ticks on screen. Rows without an id are skipped.
`idKey` names the identifying field for rows that do not call it `id`.
scripts/qml-tests/tst_multi_select.qml starts with the rule's own cases and
joins qt-runtime-gate.sh and test-crates.yml.
cc
vicrodh
7d1a144c89