style(avatars): keep shared pack helpers and tests lint clean

Move the image-key implementation above tests and use fixed-size pixel chunks
in the authored-art test. Keep contract/player byte-identical across the app,
standalone Ratatui and Engine vendor. No runtime behavior changes.

Validation: shared whale crate 44 passed, 0 failed; Ratatui all-targets Clippy
and formatting passed. Prior app gate: npm test 1592 passed / 6 ignored and
check:web passed (86 Python passed / 2 disk-image fixture skips). Native actual
build and visual checks remain valid; this changes ordering and test syntax.
APPS-226.

vendor/codewhale-ratatui/assets/avatar-pack/contract.rs

@@ -222,6 +222,12 @@ pub struct RegisteredPack {
     pub pack: Pack,
 }
 
+impl RegisteredPack {
+    pub fn image_key(&self, page: usize) -> String {
+        format!("{}:{}:{}:{page}", self.key, self.content_hash, self.handle)
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -297,9 +303,3 @@ mod tests {
         assert!(p.validate_png(&[]).is_err());
     }
 }
-
-impl RegisteredPack {
-    pub fn image_key(&self, page: usize) -> String {
-        format!("{}:{}:{}:{page}", self.key, self.content_hash, self.handle)
-    }
-}

vendor/codewhale-ratatui/assets/whale-girl/player.rs

@@ -62,9 +62,12 @@ mod tests {
             );
             for index in &clip.frames {
                 let pixels = tile(*index);
-                assert!(pixels.chunks_exact(4).any(|p| p[3] > 200), "{act} paints");
                 assert!(
-                    pixels.chunks_exact(4).any(|p| p[3] == 0),
+                    pixels.as_chunks::<4>().0.iter().any(|p| p[3] > 200),
+                    "{act} paints"
+                );
+                assert!(
+                    pixels.as_chunks::<4>().0.iter().any(|p| p[3] == 0),
                     "{act} is transparent"
                 );
             }