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/android/os.py

@@ -316,20 +316,30 @@ class Process(Stub):
         return _os.getpid()
 
     @staticmethod
-    def killProcess(pid: int):
-        pass
+    def killProcess(pid):
+        import signal
+        try:
+            _os.kill(pid, signal.SIGKILL)
+        except (OSError, ProcessLookupError):
+            pass
 
     @staticmethod
-    def sendSignal(pid: int, signal: int):
-        pass
+    def sendSignal(pid, signal_num):
+        try:
+            _os.kill(pid, signal_num)
+        except (OSError, ProcessLookupError):
+            pass
 
     @staticmethod
     def setThreadPriority(priority: int):
         pass
 
     @staticmethod
-    def setThreadPriority(tid: int, priority: int):
-        pass
+    def setThreadPriority(tid, priority):
+        try:
+            _os.setpriority(_os.PRIO_PROCESS, tid, priority)
+        except (OSError, PermissionError):
+            pass
 
     @staticmethod
     def getElapsedCpuTime() -> int:
@@ -1925,20 +1935,53 @@ class FileUtils(Stub):
     """FileUtils — 文件工具"""
 
     @staticmethod
-    def readFileToString(file: Any) -> str:
-        return ""
+    def readFileToString(path):
+        try:
+            with open(path, "r", encoding="utf-8") as f:
+                return f.read()
+        except Exception:
+            return ""
 
     @staticmethod
-    def stringToFile(file: Any, string: str):
-        pass
+    def stringToFile(path, content):
+        try:
+            with open(path, "w", encoding="utf-8") as f:
+                f.write(content)
+            return True
+        except Exception:
+            return False
 
     @staticmethod
-    def copyFile(src: Any, dest: Any) -> bool:
-        return True
+    def copyFile(src, dst):
+        try:
+            import shutil
+            shutil.copy2(src, dst)
+            return True
+        except Exception:
+            return False
 
     @staticmethod
-    def deleteDirectory(dir_: Any) -> bool:
-        return True
+    def deleteDirectory(path):
+        try:
+            import shutil
+            shutil.rmtree(path)
+            return True
+        except Exception:
+            return False
+
+    @staticmethod
+    def deleteContents(path):
+        try:
+            import shutil
+            for entry in _os.listdir(path):
+                full = _os.path.join(path, entry)
+                if _os.path.isdir(full):
+                    shutil.rmtree(full)
+                else:
+                    _os.remove(full)
+            return True
+        except Exception:
+            return False
 
     @staticmethod
     def deleteOlderFiles(dir_: Any, min_count: int, min_age_ms: int):