extract shared mosis-core library from sandbox APIs

Create core/ directory with platform-agnostic sandbox components:
- Timer manager, JSON API, Crypto API, Virtual FS
- Lua sandbox, Permission gate, Audit log, Rate limiter
- Platform abstraction interfaces (IAssetInterface, IFilesystemInterface)
- Platform-agnostic logger with Android/Desktop implementations

Update designer to link against mosis-core library instead of
including sandbox sources directly.

This is the foundation for unifying the Android service and
desktop designer to share the same codebase.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

core/include/mosis/sandbox/permission_gate.h

@@ -0,0 +1,73 @@
+#pragma once
+
+#include <string>
+#include <vector>
+#include <unordered_set>
+#include <unordered_map>
+#include <chrono>
+
+struct lua_State;
+
+namespace mosis {
+
+struct SandboxContext;  // Forward declaration
+
+enum class PermissionCategory {
+    Normal,     // Auto-granted when declared (e.g., internet, vibrate)
+    Dangerous,  // Requires user consent (e.g., camera, location)
+    Signature   // System apps only (e.g., system.settings)
+};
+
+struct PermissionInfo {
+    PermissionCategory category;
+    std::string description;
+};
+
+class PermissionGate {
+public:
+    explicit PermissionGate(const SandboxContext& context);
+
+    // Check if app has permission (throws Lua error if not)
+    bool Check(lua_State* L, const std::string& permission);
+
+    // Check without throwing (returns false if denied)
+    bool HasPermission(const std::string& permission) const;
+
+    // Get permission category
+    static PermissionCategory GetCategory(const std::string& permission);
+
+    // Get permission info (returns nullptr if unknown)
+    static const PermissionInfo* GetPermissionInfo(const std::string& permission);
+
+    // User gesture tracking
+    void RecordUserGesture();
+    bool HasRecentUserGesture(int ms = 5000) const;
+
+    // Runtime permission grant (called after user consent)
+    void GrantPermission(const std::string& permission);
+    void RevokePermission(const std::string& permission);
+
+    // Get all declared permissions
+    const std::vector<std::string>& GetDeclaredPermissions() const;
+
+    // Get all granted permissions
+    std::vector<std::string> GetGrantedPermissions() const;
+
+    // Check if permission is declared in manifest
+    bool IsDeclared(const std::string& permission) const;
+
+private:
+    const SandboxContext& m_context;
+    std::unordered_set<std::string> m_runtime_grants;  // Runtime-granted dangerous perms
+    std::chrono::steady_clock::time_point m_last_gesture;
+
+    bool CheckNormalPermission(const std::string& permission) const;
+    bool CheckDangerousPermission(const std::string& permission) const;
+    bool CheckSignaturePermission(const std::string& permission) const;
+};
+
+} // namespace mosis
+
+// Convenience alias
+using PermissionGate = mosis::PermissionGate;
+using PermissionCategory = mosis::PermissionCategory;