optimize song usage

README.md

@@ -8,6 +8,14 @@ If `songUsage` needs to be rebuilt from all existing shows, log in with a user t
 await window.wgeneratorAdmin.rebuildSongUsage()
 ```
 
+If the `songIds` index on shows needs to be backfilled for tooltip usage in song details, run:
+
+```js
+await window.wgeneratorAdmin.rebuildShowSongIds()
+```
+
+The command logs progress in the browser console while it runs and prints the final summary when finished.
+
 The migration:
 
 - resets `songUsage` for all users
@@ -16,4 +24,11 @@ The migration:
 
 It returns a summary object with processed user, show and show-song counts.
 
+The show index migration:
+
+- scans all shows and all `shows/{id}/songs` entries
+- writes the distinct `songIds` array to each show document
+
+It returns a summary object with processed show and show-song counts.
+
 This is intended as a manual one-off migration and is read-heavy by design.