Add Week 9 Smart Features: collections, artwork, predictive prefetch

Smart Collections (musicfs-search/src/collections.rs):
- CollectionStore with thread-safe Mutex<Connection>
- CollectionQuery enum: Match, DateRange, RecentlyAdded/Played, MostPlayed, Genre, Compound
- Builtin collections for Recently Added, 80s/90s Music

Artwork Extraction & Caching:
- ArtworkExtractor using symphonia Visual (musicfs-metadata)
- ArtworkCache with CAS storage + on-demand resize (musicfs-cache)
- ArtType: Front/Back/Other, ArtSize: Thumbnail/Medium/Full

Predictive Prefetching:
- PatternStore tracks access patterns with sequence prediction
- PrefetchEngine listens to FileAccessed events, prefetches predictions
- PrefetchOps exposes /.prefetch/ virtual directory with status/hints

Oracle review fixes applied:
- CollectionStore uses Mutex for thread safety
- FileAccessed event now includes file_id for canonical correlation
- JSON parse warnings in collection deserialization

130 tests pass (15 new tests added)

musicfs/crates/musicfs-metadata/Cargo.toml

@@ -8,3 +8,4 @@ musicfs-core = { path = "../musicfs-core" }
 symphonia.workspace = true
 thiserror.workspace = true
 tracing.workspace = true
+image.workspace = true

musicfs/crates/musicfs-metadata/src/artwork.rs

@@ -0,0 +1,116 @@
+use image::ImageFormat;
+use std::io::Cursor;
+use symphonia::core::meta::Visual;
+use tracing::debug;
+
+#[derive(Debug, Clone)]
+pub struct Artwork {
+    pub art_type: ArtType,
+    pub mime_type: String,
+    pub width: u32,
+    pub height: u32,
+    pub data: Vec<u8>,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum ArtType {
+    Front,
+    Back,
+    Other,
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum ArtSize {
+    Thumbnail,
+    Medium,
+    Full,
+}
+
+impl ArtSize {
+    pub fn max_dimension(&self) -> Option<u32> {
+        match self {
+            ArtSize::Thumbnail => Some(150),
+            ArtSize::Medium => Some(300),
+            ArtSize::Full => None,
+        }
+    }
+}
+
+pub struct ArtworkExtractor;
+
+impl ArtworkExtractor {
+    pub fn extract_from_visual(visual: &Visual) -> Option<Artwork> {
+        let data = visual.data.to_vec();
+
+        let img = image::load_from_memory(&data).ok()?;
+
+        let art_type = match visual.usage {
+            Some(symphonia::core::meta::StandardVisualKey::FrontCover) => ArtType::Front,
+            Some(symphonia::core::meta::StandardVisualKey::BackCover) => ArtType::Back,
+            _ => ArtType::Other,
+        };
+
+        let mime_type = if visual.media_type.is_empty() {
+            "image/jpeg".to_string()
+        } else {
+            visual.media_type.clone()
+        };
+
+        Some(Artwork {
+            art_type,
+            mime_type,
+            width: img.width(),
+            height: img.height(),
+            data,
+        })
+    }
+
+    pub fn resize(artwork: &Artwork, size: ArtSize) -> Option<Artwork> {
+        let max_dim = size.max_dimension()?;
+
+        if artwork.width <= max_dim && artwork.height <= max_dim {
+            return Some(artwork.clone());
+        }
+
+        let img = image::load_from_memory(&artwork.data).ok()?;
+        let resized = img.thumbnail(max_dim, max_dim);
+
+        let mut output = Vec::new();
+        let mut cursor = Cursor::new(&mut output);
+        resized.write_to(&mut cursor, ImageFormat::Jpeg).ok()?;
+
+        debug!(
+            "Resized artwork from {}x{} to {}x{}",
+            artwork.width,
+            artwork.height,
+            resized.width(),
+            resized.height()
+        );
+
+        Some(Artwork {
+            art_type: artwork.art_type,
+            mime_type: "image/jpeg".to_string(),
+            width: resized.width(),
+            height: resized.height(),
+            data: output,
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_art_size_dimensions() {
+        assert_eq!(ArtSize::Thumbnail.max_dimension(), Some(150));
+        assert_eq!(ArtSize::Medium.max_dimension(), Some(300));
+        assert_eq!(ArtSize::Full.max_dimension(), None);
+    }
+
+    #[test]
+    fn test_art_type_equality() {
+        assert_eq!(ArtType::Front, ArtType::Front);
+        assert_ne!(ArtType::Front, ArtType::Back);
+    }
+}

musicfs/crates/musicfs-metadata/src/lib.rs

@@ -1,3 +1,5 @@
+pub mod artwork;
 mod parser;
 
+pub use artwork::{ArtSize, ArtType, Artwork, ArtworkExtractor};
 pub use parser::MetadataParser;