Baseline: full tree snapshot after git repository loss

The previous .git directory was found gutted (only info/ remained), so
history is unrecoverable locally. This commit restores version control
with the tree exactly as it stands: the working app, the preview-tracks
launcher on the artist hero, the scrollable-track-previews design bundle
(docs + approved mockups), and the Phase 0 validation artifacts.

crates/metadata/examples/decode_to_png.rs

@@ -0,0 +1,26 @@
+//! Decode an image with the exact decoder the hero pipeline uses (the `image`
+//! crate) and write lossless PNG. Lets the live-GPU hero prototype consume
+//! bit-identical pixels to the baked path — browsers decode JPEG chroma
+//! differently, which showed up as a subtle tint in A/B comparisons.
+//!
+//! Usage: decode_to_png <input.jpg> <output.png>
+
+fn main() {
+    let mut args = std::env::args().skip(1);
+    let (Some(input), Some(output)) = (args.next(), args.next()) else {
+        eprintln!("usage: decode_to_png <input> <output.png>");
+        std::process::exit(2);
+    };
+    let bytes = std::fs::read(&input).expect("read input");
+    let decoded = image::load_from_memory(&bytes).expect("decode");
+    decoded
+        .save_with_format(&output, image::ImageFormat::Png)
+        .expect("write png");
+    println!(
+        "{} {}x{} -> {}",
+        input,
+        decoded.width(),
+        decoded.height(),
+        output
+    );
+}