feat: 全面完善API — 补全核心类方法、存根转真实实现、Exception体系扩展

核心类方法补全:
- Activity: +20方法 (requestWindowFeature, setTitle/getTitle, onKeyDown/onKeyUp, enterPictureInPictureMode, getReferrer, isTaskRoot, navigateUpTo等)
- Fragment: +15方法 (getChildFragmentManager, getParentFragment, requireContext/requireActivity, setMenuVisibility等)
- Intent: +20方法 (getParcelableExtra, setComponent/getComponent, getDataString, getScheme, putExtras等)
- View: +20方法 (setLabelFor, setRotationX/Y, setForeground, setBackgroundTintList等)
- KeyEvent: +7方法 (getCharacters, isSystem, isPrintingKey, isModifierKey, startTracking等)
- Paint: +12方法 (setStrokeCap/Join, getTextBounds, setBlendMode, setLetterSpacing等)
- Notification.Builder: +10方法 (setProgress, setShowWhen, setOnlyAlertOnce, setSound等)

存根转真实实现:
- TrafficStats: 读取 /proc/net/dev 返回真实网络流量
- RecyclerView.Adapter: 观察者模式触发通知
- BaseAdapter: 观察者模式触发通知
- ExifInterface: 使用PIL实现图片翻转/旋转
- Process: 使用os.kill实现进程信号
- FileUtils: 真实文件I/O
- SharedPreferences: 监听器模式
- TelephonyManager.listen: 维护监听器列表
- ScrollView.smoothScrollTo: 更新滚动位置

Exception体系扩展:
- 新增15个Exception/Error类 (ClassNotFoundException, IllegalAccessException, InstantiationException, InvocationTargetException, NoSuchElementException, AssertionError, OutOfMemoryError, StackOverflowError, NoClassDefFoundError, UnsatisfiedLinkError, LinkageError, VerifyError, AbstractMethodError, IncompatibleClassChangeError, ExceptionInInitializerError)

Math/System/Thread/StringBuilder/Integer增强:
- Math: +20方法 (subtractExact, multiplyExact, toIntExact, floorDiv/floorMod, fma等)
- System: getProperties/setProperties/mapLibraryName/getLogger
- Thread: +10方法 (getUncaughtExceptionHandler, getAllStackTraces, getStackTrace, holdLock等)
- StringBuilder: +7方法 (ensureCapacity, trimToSize, setLength, subSequence等)
- Integer: +8静态方法 (compare, compareUnsigned, divideUnsigned, sum, max, min等)

修复:
- app_fragment.py: 使用java.lang.IllegalStateException替代本地定义
- content_intent.py: Intent.setData/getScheme正确从Uri提取scheme
- view_ext.py: KeyEvent继承view.KeyEvent获取所有KEYCODE常量
- __init__.py: 补全Fragment/KeyEvent/MotionEvent/TrafficStats/RecyclerView等导出

统计: 221模块, 3660类, 30826方法, 180217行

android_pyapi/java/util.py

@@ -1848,6 +1848,60 @@ class Collections:
 
         return _LifoQueue(deque)
 
+    @staticmethod
+    def addAll(collection, *elements):
+        for e in elements:
+            collection.add(e)
+        return len(elements) > 0
+
+    @staticmethod
+    def emptyList():
+        return []
+
+    @staticmethod
+    def emptySet():
+        return set()
+
+    @staticmethod
+    def emptyMap():
+        return {}
+
+    @staticmethod
+    def reverseOrder(comparator=None):
+        if comparator is None:
+            return lambda a, b: -1 if a < b else (1 if a > b else 0)
+        return lambda a, b: -comparator(a, b)
+
+    @staticmethod
+    def singletonSet(element):
+        s = HashSet()
+        s.add(element)
+        return s
+
+    @staticmethod
+    def checkedList(lst, type_):
+        return lst
+
+    @staticmethod
+    def checkedSet(s, type_):
+        return s
+
+    @staticmethod
+    def checkedMap(m, keyType, valueType):
+        return m
+
+    @staticmethod
+    def unmodifiableCollection(c):
+        return c
+
+    @staticmethod
+    def unmodifiableQueue(q):
+        return q
+
+    @staticmethod
+    def unmodifiableDeque(d):
+        return d
+
 
 # ============================================================
 # Arrays
@@ -2334,6 +2388,37 @@ class Calendar(Stub):
     def getInstance() -> 'GregorianCalendar':
         return GregorianCalendar()
 
+    def clear(self, field=None):
+        if field is None:
+            self._fields = {}
+        else:
+            if field in self._fields:
+                del self._fields[field]
+
+    def isSet(self, field):
+        return field in self._fields
+
+    def getCalendarType(self):
+        return "gregory"
+
+    @staticmethod
+    def getAvailableLocales():
+        from .util import Locale
+        return [Locale.US, Locale.CHINA, Locale.JAPAN, Locale.KOREA, Locale.GERMANY, Locale.FRANCE]
+
+    def toInstant(self):
+        from .time import Instant
+        return Instant.ofEpochMilli(self.getTimeInMillis())
+
+    def getWeekYear(self):
+        return self.get(Calendar.YEAR)
+
+    def isWeekDateSupported(self):
+        return False
+
+    def getWeeksInWeekYear(self):
+        return 52
+
 
 class GregorianCalendar(Calendar):
     """java.util.GregorianCalendar"""