fix: prevent double-tap save, add subtasks at creation, fix keyboard overlap (#7, #8, #6)

- Add saving guard to prevent duplicate task creation on rapid taps
- Add pending subtasks UI to new task screen with local add/remove
- Wrap both task screens in KeyboardAvoidingView with scrollToEnd on subtask focus

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/task/[id].tsx

@@ -1,4 +1,4 @@
-import { useEffect, useState } from 'react';
+import { useEffect, useState, useRef } from 'react';
 import {
   View,
   Text,
@@ -8,6 +8,7 @@ import {
   useColorScheme,
   Alert,
   Platform,
+  KeyboardAvoidingView,
 } from 'react-native';
 import { useRouter, useLocalSearchParams } from 'expo-router';
 import {
@@ -79,6 +80,8 @@ export default function TaskDetailScreen() {
   const [selectedTagIds, setSelectedTagIds] = useState<string[]>([]);
   const [lists, setLists] = useState<{ id: string; name: string; color: string | null; icon: string | null; isInbox: boolean }[]>([]);
   const [selectedListId, setSelectedListId] = useState<string>('');
+  const [saving, setSaving] = useState(false);
+  const scrollRef = useRef<ScrollView>(null);
 
   useEffect(() => {
     if (!isValidUUID(id)) {
@@ -112,17 +115,23 @@ export default function TaskDetailScreen() {
   };
 
   const handleSave = async () => {
+    if (saving) return;
     if (!task || !title.trim()) return;
-    await updateTask(task.id, {
-      title: title.trim(),
-      notes: notes.trim() || undefined,
-      priority,
-      dueDate,
-      recurrence,
-      listId: selectedListId,
-    });
-    await setTagsForTask(task.id, selectedTagIds);
-    router.back();
+    setSaving(true);
+    try {
+      await updateTask(task.id, {
+        title: title.trim(),
+        notes: notes.trim() || undefined,
+        priority,
+        dueDate,
+        recurrence,
+        listId: selectedListId,
+      });
+      await setTagsForTask(task.id, selectedTagIds);
+      router.back();
+    } catch {
+      setSaving(false);
+    }
   };
 
   const handleDelete = () => {
@@ -196,13 +205,14 @@ export default function TaskDetailScreen() {
           <Pressable onPress={handleDelete} className="mr-3 p-1">
             <Trash2 size={20} color={colors.terracotta.DEFAULT} />
           </Pressable>
-          <Pressable onPress={handleSave} className="rounded-lg bg-bleu px-4 py-1.5">
+          <Pressable onPress={handleSave} disabled={saving} className={`rounded-lg bg-bleu px-4 py-1.5 ${saving ? 'opacity-50' : ''}`}>
             <Text className="text-sm text-white" style={{ fontFamily: 'Inter_600SemiBold' }}>{t('common.save')}</Text>
           </Pressable>
         </View>
       </View>
 
-      <ScrollView className="flex-1 px-4 pt-4" keyboardShouldPersistTaps="handled">
+      <KeyboardAvoidingView className="flex-1" behavior={Platform.OS === 'ios' ? 'padding' : 'height'}>
+      <ScrollView ref={scrollRef} className="flex-1 px-4 pt-4" keyboardShouldPersistTaps="handled">
         {/* Title */}
         <TextInput
           value={title}
@@ -391,6 +401,7 @@ export default function TaskDetailScreen() {
             value={newSubtask}
             onChangeText={setNewSubtask}
             onSubmitEditing={handleAddSubtask}
+            onFocus={() => setTimeout(() => scrollRef.current?.scrollToEnd({ animated: true }), 300)}
             placeholder={t('task.addSubtask')}
             placeholderTextColor={isDark ? '#A0A0A0' : '#6B6B6B'}
             className={`ml-2 flex-1 text-base ${isDark ? 'text-[#F5F5F5]' : 'text-[#1A1A1A]'}`}
@@ -398,8 +409,9 @@ export default function TaskDetailScreen() {
           />
         </View>
 
-        <View className="h-24" />
+        <View className="h-32" />
       </ScrollView>
+      </KeyboardAvoidingView>
     </View>
   );
 }

app/task/new.tsx

@@ -1,4 +1,4 @@
-import { useState, useEffect } from 'react';
+import { useState, useEffect, useRef } from 'react';
 import {
   View,
   Text,
@@ -7,10 +7,11 @@ import {
   ScrollView,
   useColorScheme,
   Platform,
+  KeyboardAvoidingView,
 } from 'react-native';
 import { useRouter, useLocalSearchParams } from 'expo-router';
 import {
-  X, Calendar, Repeat,
+  X, Calendar, Repeat, Plus,
   List, ShoppingCart, Briefcase, Home, Heart, Star, BookOpen,
   GraduationCap, Dumbbell, Utensils, Plane, Music, Code, Wrench,
   Gift, Camera, Palette, Dog, Leaf, Zap,
@@ -55,6 +56,10 @@ export default function NewTaskScreen() {
   const [recurrence, setRecurrence] = useState<string | null>(null);
   const [availableTags, setAvailableTags] = useState<{ id: string; name: string; color: string }[]>([]);
   const [selectedTagIds, setSelectedTagIds] = useState<string[]>([]);
+  const [saving, setSaving] = useState(false);
+  const [pendingSubtasks, setPendingSubtasks] = useState<string[]>([]);
+  const [newSubtask, setNewSubtask] = useState('');
+  const scrollRef = useRef<ScrollView>(null);
 
   useEffect(() => {
     getAllLists().then(setLists);
@@ -62,7 +67,9 @@ export default function NewTaskScreen() {
   }, []);
 
   const handleSave = async () => {
+    if (saving) return;
     if (!title.trim()) return;
+    setSaving(true);
     try {
       const taskId = await createTask({
         title: title.trim(),
@@ -75,9 +82,13 @@ export default function NewTaskScreen() {
       if (selectedTagIds.length > 0) {
         await setTagsForTask(taskId, selectedTagIds);
       }
+      for (const sub of pendingSubtasks) {
+        await createTask({ title: sub, listId: selectedListId, parentId: taskId });
+      }
       router.back();
     } catch {
       // FK constraint or other DB error — fallback to inbox
+      setSaving(false);
       setSelectedListId(getInboxId());
     }
   };
@@ -87,6 +98,16 @@ export default function NewTaskScreen() {
     if (date) setDueDate(date);
   };
 
+  const handleAddPendingSubtask = () => {
+    if (!newSubtask.trim()) return;
+    setPendingSubtasks((prev) => [...prev, newSubtask.trim()]);
+    setNewSubtask('');
+  };
+
+  const handleRemovePendingSubtask = (index: number) => {
+    setPendingSubtasks((prev) => prev.filter((_, i) => i !== index));
+  };
+
   const toggleTag = (tagId: string) => {
     setSelectedTagIds((prev) =>
       prev.includes(tagId) ? prev.filter((id) => id !== tagId) : [...prev, tagId]
@@ -110,14 +131,15 @@ export default function NewTaskScreen() {
         >
           {t('task.newTask')}
         </Text>
-        <Pressable onPress={handleSave} className="rounded-lg bg-bleu px-4 py-1.5">
+        <Pressable onPress={handleSave} disabled={saving} className={`rounded-lg bg-bleu px-4 py-1.5 ${saving ? 'opacity-50' : ''}`}>
           <Text className="text-sm text-white" style={{ fontFamily: 'Inter_600SemiBold' }}>
             {t('common.save')}
           </Text>
         </Pressable>
       </View>
 
-      <ScrollView className="flex-1 px-4 pt-4" keyboardShouldPersistTaps="handled">
+      <KeyboardAvoidingView className="flex-1" behavior={Platform.OS === 'ios' ? 'padding' : 'height'}>
+      <ScrollView ref={scrollRef} className="flex-1 px-4 pt-4" keyboardShouldPersistTaps="handled">
         {/* Title */}
         <TextInput
           autoFocus
@@ -314,8 +336,52 @@ export default function NewTaskScreen() {
           </>
         )}
 
-        <View className="h-24" />
+        {/* Subtasks */}
+        <Text
+          className={`mb-2 mt-6 text-xs uppercase tracking-wide ${isDark ? 'text-[#A0A0A0]' : 'text-[#6B6B6B]'}`}
+          style={{ fontFamily: 'Inter_600SemiBold' }}
+        >
+          {t('task.subtasks')}
+        </Text>
+        {pendingSubtasks.map((sub, index) => (
+          <View
+            key={index}
+            className={`flex-row items-center border-b py-2.5 ${isDark ? 'border-[#3A3A3A]' : 'border-[#E5E7EB]'}`}
+          >
+            <View
+              className="mr-3 h-5 w-5 items-center justify-center rounded-full border-2"
+              style={{ borderColor: colors.priority.none, backgroundColor: 'transparent' }}
+            />
+            <Text
+              className={`flex-1 text-base ${isDark ? 'text-[#F5F5F5]' : 'text-[#1A1A1A]'}`}
+              style={{ fontFamily: 'Inter_400Regular' }}
+            >
+              {sub}
+            </Text>
+            <Pressable onPress={() => handleRemovePendingSubtask(index)} className="p-1">
+              <X size={16} color={isDark ? '#A0A0A0' : '#6B6B6B'} />
+            </Pressable>
+          </View>
+        ))}
+
+        {/* Add subtask */}
+        <View className="mt-2 flex-row items-center">
+          <Plus size={18} color={colors.bleu.DEFAULT} />
+          <TextInput
+            value={newSubtask}
+            onChangeText={setNewSubtask}
+            onSubmitEditing={handleAddPendingSubtask}
+            onFocus={() => setTimeout(() => scrollRef.current?.scrollToEnd({ animated: true }), 300)}
+            placeholder={t('task.addSubtask')}
+            placeholderTextColor={isDark ? '#A0A0A0' : '#6B6B6B'}
+            className={`ml-2 flex-1 text-base ${isDark ? 'text-[#F5F5F5]' : 'text-[#1A1A1A]'}`}
+            style={{ fontFamily: 'Inter_400Regular' }}
+          />
+        </View>
+
+        <View className="h-32" />
       </ScrollView>
+      </KeyboardAvoidingView>
     </View>
   );
 }