Make BLE daemon resilient to device swaps and add device-initiated refresh

- Cache invalidation: drop ~/.config/claude-usage-monitor/ble-address and remove
  the dead MAC from bluez on connect failure, so swapping ESP boards no longer
  pins the daemon to a stale factory MAC
- Scan robustness: pick first matching candidate (head -1), sanity-check cached
  content for valid MAC format, handle multiple Claude Controllers in bluez
- 5s tick + 60s poll: inner loop wakes every 5s for fast disconnect detection
  while keeping Anthropic API cadence at one minute
- Refresh-request channel: new GATT characteristic ...0004 NOTIFY, firmware
  fires once in onSubscribe when has_received_data is false; daemon subscribes
  via setsid'd dbus-monitor pipeline (process group cleanup avoids the
  bash-wait-on-job hang we hit on disconnect)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

firmware/src/ble.cpp

@@ -8,7 +8,8 @@
 // Custom GATT UUIDs for data channel
 #define SERVICE_UUID        "4c41555a-4465-7669-6365-000000000001"
 #define RX_CHAR_UUID        "4c41555a-4465-7669-6365-000000000002"  // host writes here
-#define TX_CHAR_UUID        "4c41555a-4465-7669-6365-000000000003"  // device notifies here
+#define TX_CHAR_UUID        "4c41555a-4465-7669-6365-000000000003"  // device ack/nack notifies
+#define REQ_CHAR_UUID       "4c41555a-4465-7669-6365-000000000004"  // device-initiated refresh request
 
 #define BLE_BUF_SIZE 512
 
@@ -45,11 +46,13 @@ static NimBLEHIDDevice* hid_dev = nullptr;
 static NimBLECharacteristic* input_kbd = nullptr;
 static NimBLECharacteristic* tx_char = nullptr;
 static NimBLECharacteristic* rx_char = nullptr;
+static NimBLECharacteristic* req_char = nullptr;
 
 static ble_state_t state = BLE_STATE_INIT;
 static bool need_advertise = false;
 static char rx_buf[BLE_BUF_SIZE];
 static volatile bool data_ready = false;
+static volatile bool has_received_data = false;
 static char mac_str[18];
 
 static void start_advertising() {
@@ -86,6 +89,19 @@ class RxCallbacks : public NimBLECharacteristicCallbacks {
         memcpy(rx_buf, val.c_str(), len);
         rx_buf[len] = '\0';
         data_ready = true;
+        has_received_data = true;
+    }
+};
+
+// When the daemon enables notifications on the refresh char, ask for data
+// if we have none yet. Firing on subscribe (not on connect) ensures the
+// notification isn't dropped before the daemon's CCCD write completes.
+class ReqCallbacks : public NimBLECharacteristicCallbacks {
+    void onSubscribe(NimBLECharacteristic* chr, NimBLEConnInfo& info, uint16_t subValue) override {
+        Serial.printf("BLE: req_char onSubscribe subValue=%u has_data=%d\n", subValue, has_received_data ? 1 : 0);
+        if (subValue != 0 && !has_received_data) {
+            ble_request_refresh();
+        }
     }
 };
 
@@ -128,6 +144,13 @@ void ble_init(void) {
         NIMBLE_PROPERTY::READ | NIMBLE_PROPERTY::NOTIFY
     );
 
+    req_char = svc->createCharacteristic(
+        REQ_CHAR_UUID,
+        NIMBLE_PROPERTY::NOTIFY
+    );
+    static ReqCallbacks reqCb;
+    req_char->setCallbacks(&reqCb);
+
     svc->start();
     server->start();
     start_advertising();
@@ -186,6 +209,15 @@ void ble_send_nack(void) {
     }
 }
 
+void ble_request_refresh(void) {
+    if (state == BLE_STATE_CONNECTED && req_char) {
+        uint8_t v = 0x01;
+        req_char->setValue(&v, 1);
+        req_char->notify();
+        Serial.println("BLE: refresh requested");
+    }
+}
+
 void ble_keyboard_press(uint8_t key, uint8_t modifier) {
     if (state != BLE_STATE_CONNECTED || !input_kbd) return;
     // HID report: [modifier, reserved, key1, key2, key3, key4, key5, key6]

firmware/src/ble.h

@@ -18,6 +18,7 @@ bool ble_has_data(void);
 const char* ble_get_data(void);
 void ble_send_ack(void);
 void ble_send_nack(void);
+void ble_request_refresh(void);
 
 // BLE HID keyboard
 void ble_keyboard_press(uint8_t key, uint8_t modifier);