Library: keep Delete targets clear when search hides selected items #441

A person should know which Library items Delete will affect after changing a search filter.

At #428 head a2c22152, search updates state.query and renders (events.js:152–155) while selectedUris survives. selectedObjects() resolves those URIs from the full folder map (selection.js:11–14). Delete uses that selection (events.js:332–338), and trashSelectedObjects() sends each selected URI to Runtime (actions.js:526–531). A selected item hidden by search can therefore remain a Delete target.

Done means:

• Define one visible selection rule for search changes. Either remove hidden items from the active selection or make the retained targets explicit before a destructive action.
• Cover select A, search for B, focus the results, then Delete; assert the exact URIs sent. Include mixed visible/hidden selections, zero results, clearing search and Shift+Delete.
• Keep Keep Library navigation, uploads and rendering coherent under load #428's explicit-selection and empty-selection focus behavior. Check pointer, keyboard and menu actions against the same rule.
• Add a real browser journey and a regression test whose reverted fix fails. Preserve Runtime capability/revision checks; selection only chooses the requested objects.

Follow-up to #428. Coordinate shared Library selection/menu work with #67; do not duplicate its wallpaper scope.

Acceptance record:

• Candidate: see 0.8.0: Release 0.8.0 #93. Train fixes: ff233a867, a9e707648. The Library source record records review and source-gate results at 4653ab4cb662cad4ee57a32a0c904a483bfa452a and matching train patches. The historical f674 source gate supplies separate configured source evidence.
• Installed release evidence and remaining gate: pending. Browser controls remain author-reported and the complete menu smoke retains its reported base-case failure. Prove the real browser regression/control journey and installed pointer, keyboard and menu behavior on the accepted candidate; preserve Keep Library navigation, uploads and rendering coherent under load #428's explicit-selection and empty-selection focus requirements and its Round 4 follow-up.
• Next owner: andersalm, the current issue assignee, for current-candidate qualification and installed Library acceptance.