fix(wpf): restore verified unavailable artifacts

[nicolasestrem]

Summary

• Preserve the Unavailable comparison label when live drift cannot be established.
• Allow restore selection only when that row still has a physically verified usable artifact.
• Keep missing, unreadable, and unverified artifacts blocked from restore sets.
• Restore the approved WPF flow for file and folder modules that do not provide live drift probes.

Verification

• Focused comparison and restore-set verification: 22 passed, 0 failed, 0 skipped.
• Full verification: 1,011 passed, 0 failed, 0 skipped.
• Isolated dependency-graph build succeeded with 0 warnings and 0 errors.
• Changed-file dotnet format completed successfully.
• git diff --check completed successfully.
• Added em dash lines: 0. C# and XAML em dash hits: 0.
• Windows Computer Use verified a real-format temporary snapshot from Timeline through Compare, one-module restore selection, Confirm, owner-bound final consent, Cancel, the no-changes result, and Back to Timeline.
• The canceled flow created no pre-restore folder and made no restore write.

Stack

This narrow draft PR is stacked on codex/wpf-release-hardening and should be reviewed after PR #11.