feat: allow editing synced lists, not just device-only ones

The edit pencil was gated to local lists even though rename/delete already
worked end to end for synced collections. Read-only shares keep the icon
but show it disabled, with a hint on tap explaining why.

Refs #29

app/src/main/java/de/jeanlucmakiola/agendula/ui/tasklist/TaskListScreen.kt

@@ -52,6 +52,7 @@ import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.ExtendedFloatingActionButton
 import androidx.compose.material3.Icon
 import androidx.compose.material3.IconButton
+import androidx.compose.material3.LocalContentColor
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.MediumTopAppBar
 import androidx.compose.material3.Scaffold
@@ -139,9 +140,12 @@ fun TaskListScreen(
     val list = content?.list
     val listName = list?.name
     val listId = (filter as? TaskFilter.OfList)?.listId
-    // Editing is offered for a device-only list. A collection that belongs to an
+    // Editing is offered for any writable list, device or synced — renaming and
-    // account is the server's to rename or remove, not ours.
+    // recolouring a synced collection is a server write the same sheet already
+    // handles. A read-only share keeps the icon but disables it: tapping it
+    // explains why rather than the button silently not being there.
     var editingList by rememberSaveable { mutableStateOf(false) }
+    var readOnlyHint by rememberSaveable { mutableStateOf(false) }
     val listWriteFailure by viewModel.listWriteFailure.collectAsStateWithLifecycle()
     val listDeleted by viewModel.listDeleted.collectAsStateWithLifecycle()
     // The list this screen is about is gone; there is nothing left to show.
@@ -152,6 +156,12 @@ fun TaskListScreen(
             viewModel.clearListWriteFailure()
         }
     }
+    LaunchedEffect(readOnlyHint) {
+        if (readOnlyHint) {
+            delay(4_000)
+            readOnlyHint = false
+        }
+    }
     // One add affordance, never two: a real list with the setting on gets a pinned
     // bottom quick-add bar; everything else (incl. smart lists, which have no single
     // target list) gets the floating "New task" button.
@@ -181,11 +191,20 @@ fun TaskListScreen(
                     IconButton(onClick = { showSort = true }, enabled = content != null) {
                         Icon(Icons.AutoMirrored.Rounded.Sort, contentDescription = stringResource(R.string.sort_title))
                     }
-                    if (list != null && list.isLocal) {
+                    if (list != null) {
-                        IconButton(onClick = { editingList = true }) {
+                        IconButton(
+                            onClick = {
+                                if (list.isReadOnly) readOnlyHint = true else editingList = true
+                            },
+                        ) {
                             Icon(
                                 Icons.Rounded.Edit,
                                 contentDescription = stringResource(R.string.list_edit_title),
+                                tint = if (list.isReadOnly) {
+                                    LocalContentColor.current.copy(alpha = 0.38f)
+                                } else {
+                                    LocalContentColor.current
+                                },
                             )
                         }
                     }
@@ -230,23 +249,28 @@ fun TaskListScreen(
                     .height(SnackChipHeight),
                 contentAlignment = Alignment.CenterStart,
             ) {
-                // One chip, one anchor: the undo receipt takes precedence, and a
+                // One chip, one anchor, in priority order: the undo receipt first,
-                // refused list write reports itself once the undo window is clear.
+                // then a refused list write once the undo window is clear, then the
+                // read-only edit hint — the quietest of the three, so it never
+                // outranks something the other two are actually reporting.
                 val failure = listWriteFailure
-                if (undo != null || failure == null) {
+                when {
-                    SnackChip(
+                    undo != null -> SnackChip(
-                        visible = undo != null,
+                        visible = true,
                         message = stringResource(
                             if (undo is UndoReceipt.Completed) R.string.task_completed else R.string.task_deleted,
                         ),
                         actionLabel = stringResource(R.string.undo),
                         onAction = viewModel::undo,
                     )
-                } else {
+                    failure != null -> SnackChip(
-                    SnackChip(
                         visible = true,
                         message = stringResource(listWriteFailureMessage(failure)),
                     )
+                    else -> SnackChip(
+                        visible = readOnlyHint,
+                        message = stringResource(R.string.list_read_only),
+                    )
                 }
             }
         }