M3: operations engine (copy/move/delete, progress, cancellation, conflicts) + foreground service

CHANGELOG.md

@@ -12,6 +12,20 @@ upload needs a **higher `versionCode`** than every previous upload.
 
 ### Added
 
+- **M3 — operations engine and foreground service.** `domain/FileOperations` turns the
+  backend primitives into copy, move, delete and rename: it walks folders, counts the
+  work up front so the progress bar has an honest denominator, checks for cancellation
+  between entries (never swallowing `CancellationException`), and reports per-item
+  failures instead of abandoning a batch because one file was unreadable. Conflicts are
+  resolved through the M1 `TransferPlanner` — `ASK` is deliberately surfaced to the
+  caller so the UI can prompt. A move tries the backend's atomic rename first and only
+  falls back to copy-then-delete when the backend cannot do it (the SAF path across
+  directories); the source is never deleted when its copy failed. `service/FileOpService`
+  is a `dataSync` foreground service that mirrors the engine's progress into an ongoing
+  notification, so a long operation survives the app being backgrounded. 23 new JVM
+  tests (99 total), including Robolectric coverage of the notification and the service
+  entering the foreground.
+
 - **M2 — storage layer.** The two storage backends behind one interface. `AllFilesSource`
   is `java.io.File` over every mounted volume (the "All files access" path);
   `SafSource` is the Storage Access Framework fallback, reading a persisted tree URI