The failure was not the app bar at all. Dumping the hierarchy at the point of failure showed a TextView whose text was 'Search this folder' and a desc='Clear search' beside it: the app was already in search mode, because the previous iteration left it there and CompilationMode.Ignore() reinstalls nothing between iterations. So the setup found a search field where it expected an action. openFixture now calls killProcess() before each iteration, and the test writes search-action-missing.xml into its external files directory when the action is missing, which is what turned this from a guess into a diagnosis.
With that, one run gives OK (4 tests): coldStart 531.6 ms median (475.6-552.0), opening a 1000-file folder 12 frames (12-17), scrolling it with four swipes 97 frames (92-100), and typing into search 39 frames (36-40). The run before it, same method, gave 519.5 ms / 14 / 94 / 38, so the numbers repeat. PERFORMANCE.md now carries both runs side by side and only lists what is genuinely still missing: larger folders, the photo grid, and any jank figure at all, since this phone reports frame counts and no frame durations.
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