The Overview identity fallback chain is pure logic, but it lived on the
applet root and its test extracted the function body from main.qml.
OverviewProviders.detailText now owns it beside placeholderText, the
Overview row calls the module directly, and tst_overview_selection.qml
covers the chain with direct QtTests.

Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>