fix: MetalRT STT/TTS download 404 — remove incorrect hf_subdir paths

The HF repos (runanywhere/whisper_tiny_4bit, etc.) have files at the
repo root, not in a subdirectory. The hf_subdir field was incorrectly
set, causing 404s during rcli setup.

Made-with: Cursor

Author: shubhammalhotra28

src/models/model_registry.h

@@ -304,7 +304,7 @@ inline std::vector<MetalRTComponentModel> metalrt_component_models() {
             "Whisper Tiny (MLX 4-bit)",
             "stt",
             "runanywhere/whisper_tiny_4bit",
-            "whisper-tiny-mlx-4bit",
+            "",
             "whisper-tiny-mlx-4bit",
             40,
             "Fastest transcription, lower accuracy (~10% WER)",
@@ -316,7 +316,7 @@ inline std::vector<MetalRTComponentModel> metalrt_component_models() {
             "Whisper Small (MLX 4-bit)",
             "stt",
             "runanywhere/whisper_small_4bit",
-            "whisper-small-mlx-4bit",
+            "",
             "whisper-small-mlx-4bit",
             375,
             "Good balance of speed and accuracy (~5% WER)",
@@ -328,7 +328,7 @@ inline std::vector<MetalRTComponentModel> metalrt_component_models() {
             "Whisper Medium (MLX 4-bit)",
             "stt",
             "runanywhere/whisper_medium_4bit",
-            "whisper-medium-mlx-4bit",
+            "",
             "whisper-medium-mlx-4bit",
             980,
             "Best accuracy, slower (~3% WER)",
@@ -340,7 +340,7 @@ inline std::vector<MetalRTComponentModel> metalrt_component_models() {
             "Kokoro 82M (bf16)",
             "tts",
             "runanywhere/kokoro_bf16",
-            "Kokoro-82M-bf16",
+            "",
             "Kokoro-82M-bf16",
             82,
             "Kokoro TTS for GPU-accelerated speech synthesis",