LLM: enable Qwen3-4B NPU (21 tok/s) in service pipeline

- ExecuTorchLlmEngine: eval_mode 0 (our .pte is kv-mode, not hybrid)
- KazeiaService: call llm.load() after TTS init; try/catch falls back
  to echo mode if the runner or .pte are missing.

Pipeline on device: STT(WhisperHybridEngine) → [VoiceCommands → LLM] → TTS(Qwen3TtsEngine).
Validated on OnePlus Pad 3: LLM ready in ~8 s, gen 21.3 tok/s, RSS 1.76 GB in the
qnn_llama_runner subprocess (out-of-process from the Kazeia app).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

kazeia-android/app/src/main/java/com/kazeia/llm/ExecuTorchLlmEngine.kt

@@ -9,7 +9,8 @@ import java.io.File
 /**
  * LLM Engine using ExecuTorch + QNN backend via subprocess.
  * Calls qnn_llama_runner binary with root access.
- * Qwen3-0.6B at ~90 tok/s on NPU (Snapdragon 8 Elite).
+ * Current tablet config: Qwen3-4B KV-mode, ~18-20 tok/s on Hexagon V79 (Snapdragon 8 Elite),
+ * TTFT 0.9 s, RSS 1.76 GB. Previously tested Qwen3-0.6B at ~76 tok/s.
  */
 class ExecuTorchLlmEngine(
     private val onLog: ((String) -> Unit)? = null
@@ -179,7 +180,7 @@ if [ -n "${'$'}SYSTEM_ARGS" ]; then
     --prompt "${'$'}PROMPT" \
     --temperature ${'$'}TEMP \
     --seq_len ${'$'}SEQ_LEN \
-    --eval_mode 1
+    --eval_mode 0
 else
   exec ./qnn_llama_runner \
     --model_path hybrid_llama_qnn.pte \
@@ -191,7 +192,7 @@ else
     --prompt "${'$'}PROMPT" \
     --temperature ${'$'}TEMP \
     --seq_len ${'$'}SEQ_LEN \
-    --eval_mode 1
+    --eval_mode 0
 fi
 """.trimIndent()
 

kazeia-android/app/src/main/java/com/kazeia/service/KazeiaService.kt

@@ -516,10 +516,14 @@ class KazeiaService : Service() {
                     ))
                 }
 
-                // LLM: disabled for debugging — echo mode
-                _loadingState.value = LoadingState(50, "LLM (echo mode)…")
+                // LLM: Qwen3-4B on Hexagon V79 via qnn_llama_runner.
+                _loadingState.value = LoadingState(50, "LLM Qwen3-4B NPU…")
                 llm = ExecuTorchLlmEngine { msg -> log(msg) }
-                log("LLM: disabled for debug, echo mode active")
+                try {
+                    llm.load("${KazeiaApplication.MODELS_DIR}/qwen3-4b", com.kazeia.core.LlmConfig())
+                } catch (e: Exception) {
+                    log("LLM load failed: ${e.message} — falling back to echo mode")
+                }
 
                 _loadingState.value = LoadingState(80, "Audio…")
                 // Audio
@@ -539,7 +543,8 @@ class KazeiaService : Service() {
 
                 addMessage(ChatMessage(
                     role = ChatMessage.Role.KAZEIA,
-                    text = "Bonjour, je suis Kazeia. Mode perroquet actif."
+                    text = if (llm.isLoaded()) "Bonjour, je suis Kazeia."
+                           else "Bonjour, je suis Kazeia. Mode perroquet actif."
                 ))
                 _pipelineState.value = PipelineState.Idle