T24c round 1 fix

- FileChangeCard's header wraps: the path keeps label_width, counts and
  verdict drop below as one group; MultiFileDiffReview's header wraps its
  counts and its all-buttons inside the box, parted by justify_between
- git::DiffViewer's fold rows are Tab stops with a focus ring when the
  owner opens folds; every row keeps a transparent border so heights match;
  an inert fold no longer shows a pointer
- tests: a_narrow_review_wraps_its_rows_inside_its_box,
  git::a_fold_opens_from_the_keyboard; the gallery adds a 280px review
- AGENTS: taffy drops gaps beside an auto margin; wrapping headers

TASKS.md

@@ -277,3 +277,4 @@ Per-component lines live in `tasks/`. Tags there:
 | T24a | 3 | PASS | |
 | T24b | 1 | FAIL | a task of one step crashed at render: its bar asked for one segment, and a segmented bar needs two |
 | T24b | 2 | PASS | |
+| T24c | 1 | FAIL | at 280px the path vanished and Accept all drew outside the box; the diff's fold rows took presses but no Tab |