Show a truncation notice when search hits the 1000-result cap

The search already stopped accepting results at 1000 and cancelled the
producer, but the user was never told the list had been truncated. Append
the "Search aborted, more than 1000 results found" row (a no-op to click).

Assisted-by: Claude:claude-opus-4-8:Claude Code

ILSpy/Search/RunningSearch.cs

@@ -220,6 +220,16 @@ namespace ILSpy.Search
 					// Stop the producer — anything it pushes from here would just be
 					// discarded, so why burn CPU on it.
 					cts.Cancel();
+					// Tell the user the list was truncated (appended after the sorted results; its
+					// null Reference makes it a no-op to click).
+					sink.Add(new SearchResult {
+						Name = ICSharpCode.ILSpy.Properties.Resources.SearchAbortedMoreThan1000ResultsFound,
+						Location = string.Empty,
+						Assembly = string.Empty,
+						Image = null!,
+						LocationImage = null!,
+						AssemblyImage = null!,
+					});
 				}
 				// Drain-discard any items still queued: without this the termination
 				// condition (runTask done + queue empty) never fires and the timer