T23b round 1 fixes

- source cards and web results with a handler are Tab stops with focus rings
- the sources row and a passage's header shrink with an ellipsis, keeping the
  count, chevron and score in view
- chat tests move into a folder, citations in their own file
- gallery: a narrow column of citations

TASKS.md

@@ -258,3 +258,4 @@ Per-component lines live in `tasks/`. Tags there:
 | T22 | 2 | PASS | |
 | T23a | 1 | FAIL | a long message of yours overflowed a narrow column; pictures and video sized to the theme, not their column; a finished stream kept revealing; avatar pictures from the web were read as files; the list stayed away after it fit again; the reasoning toggle had no Tab stop; a link's thumbnail lost its corners |
 | T23a | 2 | PASS | |
+| T23b | 1 | FAIL | source cards and web results with a handler were no Tab stops; in a narrow column the sources row and a passage's header ran past their edge |