perf(library): page missing-file cleanup with safe SAF batch checks

android/app/src/main/kotlin/com/zarz/spotiflac/MainActivity.kt

@@ -1115,6 +1115,13 @@ class MainActivity: FlutterFragmentActivity() {
                             }
                             result.success(exists)
                         }
+                        "safExistsBatch" -> {
+                            val urisJson = call.argument<String>("uris_json") ?: "[]"
+                            val response = withContext(Dispatchers.IO) {
+                                safExistsBatch(urisJson)
+                            }
+                            result.success(response)
+                        }
                         "isSafTreeAccessible" -> {
                             val uriStr = call.argument<String>("tree_uri") ?: ""
                             val accessible = withContext(Dispatchers.IO) {

android/app/src/main/kotlin/com/zarz/spotiflac/MainActivitySafScan.kt

@@ -1558,10 +1558,51 @@ internal fun MainActivity.scanSafTreeIncremental(
         return spill.result()
     }
 
-    /**
-     * Resolve SAF file last-modified values for a list of content URIs.
-     * Returns JSON object mapping uri -> lastModified (unix millis).
-     */
+// A failed DocumentsProvider query must never be mistaken for a missing file.
+// Unlike DocumentFile.exists(), this keeps null cursors/exceptions inconclusive.
+internal fun MainActivity.safExistsBatch(urisJson: String): String {
+    val result = JSONObject()
+    val uris = JSONArray(urisJson)
+    val accessibleTrees = mutableMapOf<String, Boolean>()
+    val permissions = contentResolver.persistedUriPermissions
+    val projection = arrayOf(DocumentsContract.Document.COLUMN_DOCUMENT_ID)
+    for (index in 0 until uris.length()) {
+        val path = uris.optString(index)
+        if (path.isBlank()) continue
+        var status = "unknown"
+        try {
+            val uri = Uri.parse(path)
+            val treeAccessible = if (DocumentsContract.isTreeUri(uri)) {
+                val treeId = DocumentsContract.getTreeDocumentId(uri)
+                val tree = DocumentsContract.buildTreeDocumentUri(uri.authority, treeId)
+                accessibleTrees.getOrPut(tree.toString()) {
+                    val granted = permissions.any { it.uri == tree && it.isReadPermission }
+                    if (!granted) false else {
+                        val root = DocumentsContract.buildDocumentUriUsingTree(tree, treeId)
+                        contentResolver.query(root, projection, null, null, null)?.use {
+                            it.moveToFirst()
+                        } == true
+                    }
+                }
+            } else false
+            contentResolver.query(uri, projection, null, null, null)?.use { cursor ->
+                status = if (cursor.moveToFirst()) "found"
+                    else if (treeAccessible &&
+                        !cursor.extras.getBoolean(DocumentsContract.EXTRA_LOADING, false))
+                        "missing" else "unknown"
+            }
+        } catch (_: Exception) {
+            // Revoked permission, offline storage and provider errors: retain row.
+        }
+        result.put(path, status)
+    }
+    return result.toString()
+}
+
+/**
+ * Resolve SAF file last-modified values for a list of content URIs.
+ * Returns JSON object mapping uri -> lastModified (unix millis).
+ */
 internal fun MainActivity.getSafFileModTimes(urisJson: String): String {
         val result = JSONObject()
         val uris = try {