refactor: centralize main session key normalization in apps

apps/android/app/src/main/java/com/clawdbot/android/NodeRuntime.kt

@@ -700,8 +700,8 @@ class NodeRuntime(context: Context) {
       val ui = config?.get("ui").asObjectOrNull()
       val raw = ui?.get("seamColor").asStringOrNull()?.trim()
       val sessionCfg = config?.get("session").asObjectOrNull()
-      val rawMainKey = sessionCfg?.get("mainKey").asStringOrNull()?.trim()
-      _mainSessionKey.value = rawMainKey?.takeIf { it.isNotEmpty() } ?: "main"
+      val mainKey = normalizeMainKey(sessionCfg?.get("mainKey").asStringOrNull())
+      _mainSessionKey.value = mainKey
 
       val parsed = parseHexColorArgb(raw)
       _seamColorArgb.value = parsed ?: DEFAULT_SEAM_COLOR_ARGB

apps/android/app/src/main/java/com/clawdbot/android/SessionKey.kt

@@ -0,0 +1,6 @@
+package com.clawdbot.android
+
+internal fun normalizeMainKey(raw: String?): String {
+  val trimmed = raw?.trim()
+  return if (!trimmed.isNullOrEmpty()) trimmed else "main"
+}

apps/android/app/src/main/java/com/clawdbot/android/voice/TalkModeManager.kt

@@ -21,6 +21,7 @@ import android.speech.tts.UtteranceProgressListener
 import android.util.Log
 import androidx.core.content.ContextCompat
 import com.clawdbot.android.bridge.BridgeSession
+import com.clawdbot.android.normalizeMainKey
 import java.net.HttpURLConnection
 import java.net.URL
 import java.util.UUID
@@ -814,7 +815,7 @@ class TalkModeManager(
       val config = root?.get("config").asObjectOrNull()
       val talk = config?.get("talk").asObjectOrNull()
       val sessionCfg = config?.get("session").asObjectOrNull()
-      val mainKey = sessionCfg?.get("mainKey").asStringOrNull()?.trim()?.takeIf { it.isNotEmpty() } ?: "main"
+      val mainKey = normalizeMainKey(sessionCfg?.get("mainKey").asStringOrNull())
       val voice = talk?.get("voiceId")?.asStringOrNull()?.trim()?.takeIf { it.isNotEmpty() }
       val aliases =
         talk?.get("voiceAliases").asObjectOrNull()?.entries?.mapNotNull { (key, value) ->