Bug: itemviewer-ui-thread-marshalling-divergence

[drmoisan]

• Work Mode: full-bug

Summary

The ItemViewer type exposes three different UI-thread seams and the codebase uses all three, with
one operation marshalled onto a WPF Dispatcher that may never be pumped and another marshalled not
at all. Out of scope under epic #136's no-behavior-change NFR.

Environment

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Steps to Reproduce

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Expected Behavior

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Actual Behavior

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Logs / Screenshots

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Impact / Severity

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Source

From: docs/features/potential/2026-08-07-itemviewer-ui-thread-marshalling-divergence.md