Refine semantic search and CPU fallback

- make Candle CUDA support opt-in so default builds work on CPU-only machines
- improve semantic search loading and empty states in the gallery
- keep semantic search UX clearer when no matches are found

Refs: #4

src-tauri/Cargo.toml

@@ -12,6 +12,10 @@ crate-type = ["staticlib", "cdylib", "rlib"]
 [build-dependencies]
 tauri-build = { version = "2", features = [] }
 
+[features]
+default = []
+candle-cuda = ["candle-core/cuda", "candle-nn/cuda", "candle-transformers/cuda"]
+
 [dependencies]
 tauri = { version = "2", features = ["protocol-asset"] }
 tauri-plugin-opener = "2"
@@ -35,8 +39,8 @@ log = "0.4"
 ffmpeg-sidecar = "2.5.0"
 xxhash-rust = { version = "0.8", features = ["xxh3"] }
 sysinfo = "0.38.4"
-candle-core = { version = "0.10.2", features = ["cuda"] }
-candle-nn = { version = "0.10.2", features = ["cuda"] }
-candle-transformers = { version = "0.10.2", features = ["cuda"] }
+candle-core = "0.10.2"
+candle-nn = "0.10.2"
+candle-transformers = "0.10.2"
 hf-hub = { version = "0.5.0", default-features = false, features = ["ureq", "native-tls"] }
 tokenizers = "0.22.1"

src-tauri/src/embedder.rs

@@ -84,21 +84,18 @@ impl ClipImageEmbedder {
 }
 
 fn resolve_device() -> Result<Device> {
-    let cuda_device = Device::cuda_if_available(0)?;
-    if cuda_device.is_cuda() {
-        println!("CLIP embedder using CUDA device.");
-        return Ok(cuda_device);
-    }
-
-    #[cfg(target_os = "macos")]
+    #[cfg(feature = "candle-cuda")]
     {
-        let metal_device = Device::metal_if_available(0)?;
-        if metal_device.is_metal() {
-            println!("CLIP embedder using Metal device.");
-            return Ok(metal_device);
+        let cuda_device = Device::cuda_if_available(0)?;
+        if cuda_device.is_cuda() {
+            println!("CLIP embedder using CUDA device.");
+            return Ok(cuda_device);
         }
     }
 
+    #[cfg(not(feature = "candle-cuda"))]
+    println!("CLIP embedder built without CUDA support.");
+
     println!("CLIP embedder using CPU device.");
     Ok(Device::Cpu)
 }