Two seconds of readdir and stat cannot be made much cheaper - each is a round trip to another process - so the folder is now read in batches and drawn as it arrives. StorageSource.listBatches hands over 200 entries at a time; AllFilesSource implements it with Files.newDirectoryStream, which is lazy where File.listFiles materialised the whole directory first; the default implementation is one batch, so the SAF backend and every test fake are unchanged.
BrowserViewModel.load merges each batch into the list already on screen with core/SortedMerge, which is O(n+k) rather than re-sorting the folder on every batch, and keeps the rows in the user's order at every moment instead of shuffling them into place when the last batch lands. loading stays true until the last batch, so the progress bar the screen already draws sits above rows that are already useful. publishEntries is separate from recompute for that reason: the merge has done the ordering, and the batch path only has to apply the hidden filter.
Tests: four for the merge (including ties not jumping ahead) and one for the batched read, which asserts 250 files arrive as 100+100+50 covering every entry exactly once - the thing a streaming read is easiest to get wrong about. PERFORMANCE.md records the expected effect and states plainly that it is not measured yet, since confirming it needs the 20000-file fixture rebuilt.
SoftwareApp
cb47090e11