library: the page lit by its own records, and portraits that prove out

The expander reserves once on the page root instead of standing min-heights
on the grid; shelf heads carry artist portraits keyed by path; every record
tints its own card, expander and glow from its cover; the artwork opens the
shared viewer; the banner wash reads the playing record and actually paints
(isolation, the artist page's own fix); descriptions animate on both pages
via partAnim. Portrait resolution rejects placeholder rows and never stores
a silhouette (pick_artist_portrait, 3 tests); repair re-resolves the missing.

crates/library/src/lib.rs

@@ -288,6 +288,21 @@ impl Library {
         Ok(())
     }
 
+    /// One row per distinct album artist, with whatever portrait path is
+    /// stored against it. The caller decides what counts as missing — the
+    /// library has no view of the filesystem, and a path that is present in the
+    /// database but gone from disk is exactly the case worth repairing.
+    pub fn artist_portraits(&self) -> Result<Vec<(String, Option<String>)>> {
+        let conn = self.conn.lock().unwrap();
+        let mut stmt = conn.prepare(
+            "SELECT artist, MAX(artist_art_path) FROM albums GROUP BY artist COLLATE NOCASE",
+        )?;
+        let rows = stmt
+            .query_map([], |r| Ok((r.get(0)?, r.get(1)?)))?
+            .collect::<std::result::Result<Vec<_>, _>>()?;
+        Ok(rows)
+    }
+
     pub fn set_artist_art(&self, artist: &str, art_path: &str) -> Result<usize> {
         let conn = self.conn.lock().unwrap();
         Ok(conn.execute(