feat(keyboard): ship AI mode surface with streaming search answers

Add the AI keyboard tab, Agent settings, and user-owned LLM key path for 1.7.0, including streaming answers and web-search transports without the built-in DeepSeek fallback.

OSGKeyboardShared/Services/FlowSessionKeys.swift

@@ -94,6 +94,7 @@ public enum FlowSessionKeys {
     /// per-request timeout clamps to this value, so it participates in the
     /// keyboard-watchdog budget below.
     public static let maxPolishTimeout: TimeInterval = 35
+    public static let aiQuestionRequestTimeout: TimeInterval = 60
 
     /// Extra slack for result serialization, cross-process propagation, and
     /// the host's own polling cadence.
@@ -115,6 +116,14 @@ public enum FlowSessionKeys {
         return asrWait + batchASRFallbackTimeout + maxPolishTimeout + resultDeliveryMargin
     }
 
+    public static func keyboardAIResultTimeout(engineMode: String) -> TimeInterval {
+        let asrWait = engineMode == "local" ? localASRWaitTimeout : cloudASRWaitTimeout
+        return asrWait
+            + batchASRFallbackTimeout
+            + aiQuestionRequestTimeout
+            + resultDeliveryMargin
+    }
+
     public enum RecordingState: String, Sendable, Equatable {
         case idle
         case recording