feat(ble): expose isInitialized and reclaim memory before radios start

The controller and the WiFi driver each need a large aggregate allocation,
which a live app sitting on garbage can deny - that is why a failed connect
often succeeded on retry. Both bindings now collect before initializing, and
the tree reserves its node and spec capacity so a build does not reallocate
into a tight heap.

native/include/lua/layout.h

@@ -131,10 +131,17 @@ public:
   const char* error = nullptr;
   uint16_t focus = NONE;
 
+  // Growth doubling needs the old and new buffers live at once, which is the
+  // allocation that fails first on a tight heap. One reservation covers a
+  // typical screen so a build reallocates only if it genuinely gets large.
+  static constexpr size_t RESERVE = 64;
+
   void reset() {
     focus = NONE;
     nodes.clear();
     specs.clear();
+    nodes.reserve(RESERVE);
+    specs.reserve(RESERVE);
     labelAt.clear();
     labels.clear();
     styles.clear();

native/include/lua/providers.h

@@ -231,6 +231,7 @@ public:
   virtual ~BleProvider() = default;
   virtual Status init(const std::string* name) = 0;
   virtual void deinit() = 0;
+  virtual bool isInitialized() const = 0;
   virtual Status scan(int32_t durationMs, std::vector<BleDevice>& devices) = 0;
   virtual Status connect(const std::string& address) = 0;
   virtual void disconnect() = 0;