[SimonCropp]

On Windows, the tray's Update stops whatever runs from the tray's store before it updates, since a file in use can't be replaced. That includes a viewer started from the tray's own viewer folder. A viewer that held the inline queue holds it in memory and stages it only as it exits, so being stopped lost every snapshot in it. The docs said to accept or close what was pending before updating.

The change.

• ListenerTable.Owner(port) returns the id of the process listening on a port. It comes from the same row of Windows' listener table that ListenerTable already reads, which ends with the owning process's id in both layouts. It returns null off Windows, or wherever the table can't be read.
• TrayUpdate.Start, once the update's shell has started and before the tray exits, calls TrayUpdate.CloseOwningViewer. That:
  • finds whoever listens on the viewer port;
  • passes over this tray itself, whose own queue it stages as it exits;
  • checks whether that process's image is somewhere the update stops (TrayUpdate.Stops: under the store or AlsoStopUnder, ignoring case, by whole folders);
  • if it is, sends it Quit and waits up to fifteen seconds for it to go. The shell waits thirty for the tray.
• No protocol change. A Quit from the wire already makes a viewer that owns the queue exit, whatever a tray says, and the viewer stages its queue on the way out. Only a close by hand hides the window beside a tray.
• A viewer from anywhere else, such as DiffEngine's own bundle, is left alone, since nothing stops it.
• Docs: the tray page's Update section and CLAUDE.md say what happens now.

Tests.

• ListenerTableTests.AListenerSaysWhoseItIs: this process, for a listener of either family, and null once it stops.
• TrayUpdateTests.TheUpdateStopsWhatRunsFromTheStore: the store and AlsoStopUnder match, whatever the case, and a sibling folder that only starts with the same name doesn't.
• TrayUpdateTests.AViewerTheUpdateStopsIsAskedToClose: Windows PowerShell stands in for the viewer, listening on a port of its own, and the update is told to stop under PowerShell's folder. The stand-in is found by the table, sent verb: quit and has exited.
• TrayUpdateTests.AViewerTheUpdateLeavesAloneIsLeftAlone and AQueueThisTrayHoldsIsNotAskedToClose: nothing is sent.
• ViewerProgramTests.AQuitFromTheWireClosesBesideATray: with the tray's mutex held and a snapshot queued, a Close from the wire ends the loop without a frame.

Locally on Windows, a Release build had no errors, and:

• DiffEngineTray.Core.Tests passed 321, with 4 skipped.
• DiffEngineTray.Tests passed 106.
• DiffEngineViewer.Tests passed 871, with 25 skipped.
• DiffEngine.Tests passed 2,267, with 20 skipped. The 3 that failed are the ListenerTable.Enumerated ones that always fail on Windows 10.0.26300, where .NET leaves listeners out of its list; CI passes them.

Not seen working. I didn't run a real update against a real viewer holding a queue.