refactor(ENV-2899): park reconnect until .poweredOn instead of polling

Replaces the retry loop (20 × 0.5s waiting for the central manager to
become .poweredOn) with an event-driven approach: if `reconnect` is
called while the manager isn't ready, stash the call in
`pendingReconnects` and drain it from `centralManagerDidUpdateState`
when the state transitions to .poweredOn. Also fail any parked calls
on `cleanup()` so Flutter futures don't leak on shutdown.

Addresses PR review feedback that polling masked the underlying iOS
state-transition timing issue.

Author: Jacksper13

ios/Runner/Ble/BluetoothChannel.swift

@@ -62,6 +62,10 @@ class BluetoothChannel: NSObject, CBCentralManagerDelegate, FlutterStreamHandler
     private var reconnectionAttempts: Int = 0
     private var isShuttingDown = false
 
+    // Reconnect calls received before `centralManager` reaches `.poweredOn`.
+    // Drained from `handleBluetoothPoweredOn`. Only touched on `bleQueue`.
+    private var pendingReconnects: [(FlutterMethodCall, FlutterResult)] = []
+
     private let bleQueue = DispatchQueue(label: "com.envoy.ble", qos: .userInteractive)
 
     let connectOptions: [String: Any] = [
@@ -209,28 +213,30 @@ class BluetoothChannel: NSObject, CBCentralManagerDelegate, FlutterStreamHandler
     /// Reconnect to a previously paired device.
     /// prepareDevice() should be called first to register native channels.
     ///
-    /// If the central manager isn't `.poweredOn` yet (e.g. the user just
-    /// toggled Bluetooth and CoreBluetooth is still `.resetting`/`.unknown`),
-    /// we retry for up to ~10s (20 × 0.5s) waiting for `.poweredOn` before
-    /// returning `NO_CENTRAL`. Prime advertises continuously, so the phone
-    /// side was the only thing preventing recovery.
-    private func reconnect(call: FlutterMethodCall, result: @escaping FlutterResult, retriesLeft: Int = 20) {
+    /// If the central manager isn't `.poweredOn` yet (e.g. right after app
+    /// launch when CoreBluetooth is still transitioning from `.unknown`, or
+    /// after the user toggles Bluetooth while `.resetting`), the call is
+    /// parked in `pendingReconnects` and drained from
+    /// `centralManagerDidUpdateState` when the manager transitions to
+    /// `.poweredOn`. Prime advertises continuously, so the phone side is
+    /// the only thing preventing recovery.
+    private func reconnect(call: FlutterMethodCall, result: @escaping FlutterResult) {
         guard let arguments = call.arguments as? [String: Any],
               let deviceId = arguments["deviceId"] as? String,
               !deviceId.isEmpty else {
             result(FlutterError(code: "INVALID_DEVICE_ID", message: "Device ID is required", details: nil))
             return
         }
 
+        // Make sure a CBCentralManager exists so we'll get the
+        // `.poweredOn` transition that drains the parked calls.
+        setupBluetoothManager()
+
         guard let central = centralManager, central.state == .poweredOn else {
-            if retriesLeft > 0 {
-                print("\(Self.TAG) Central not ready for reconnect (\(retriesLeft) retries left); waiting 0.5s")
-                bleQueue.asyncAfter(deadline: .now() + 0.5) { [weak self] in
-                    self?.reconnect(call: call, result: result, retriesLeft: retriesLeft - 1)
-                }
-                return
+            print("\(Self.TAG) Central not ready for reconnect; parking call until .poweredOn")
+            bleQueue.async { [weak self] in
+                self?.pendingReconnects.append((call, result))
             }
-            result(FlutterError(code: "NO_CENTRAL", message: "Central manager not available or not powered on", details: nil))
             return
         }
 
@@ -371,6 +377,13 @@ class BluetoothChannel: NSObject, CBCentralManagerDelegate, FlutterStreamHandler
         // Set flag first to prevent any further Flutter channel communication
         isShuttingDown = true
 
+        // Fail any parked reconnect calls so Flutter futures don't leak.
+        let parked = pendingReconnects
+        pendingReconnects.removeAll()
+        for (_, result) in parked {
+            result(FlutterError(code: "NO_CENTRAL", message: "Bluetooth channel shutting down", details: nil))
+        }
+
         // Stop any pending reconnection timers
         stopReconnection()
 
@@ -731,6 +744,17 @@ class BluetoothChannel: NSObject, CBCentralManagerDelegate, FlutterStreamHandler
     }
 
     private func handleBluetoothPoweredOn(central: CBCentralManager) {
+        // Drain any reconnect calls that arrived before the central was ready.
+        // Already on `bleQueue` here, so no dispatch is needed.
+        if !pendingReconnects.isEmpty {
+            let parked = pendingReconnects
+            pendingReconnects.removeAll()
+            print("\(Self.TAG) Draining \(parked.count) parked reconnect call(s)")
+            for (call, result) in parked {
+                reconnect(call: call, result: result)
+            }
+        }
+
         // Rebuild pairedAccessories from current session state.
         var sessionPaired: [UUID: ASAccessory] = [:]
         for accessory in session.accessories {