Filter the people rail in the query, and count the unassigned faces

`faces::people` grouped `face_person` after a LEFT JOIN over every person
and sorted the lot by name; the rail then discarded the empty, unnamed
groups a regrouping pass leaves behind — 17,000 of 19,000 rows on the
reference library. `people_in_use` filters them in the WHERE and joins
`people` to face counts aggregated first (2,000 groups), so the sort sees
only the rows that will be drawn. `count_unassigned` replaces fetching
2,400 ids to take their length. `load_people` 22 ms → 10 ms.

ui/dr-ui/src/identity.rs

@@ -216,7 +216,9 @@ pub struct IdentityView {
 /// Filtered rather than deleted, because this is a screen being drawn and not a
 /// catalog being repaired. A row is withheld; nothing is lost, a sync cannot
 /// resurrect what was never removed, and the prune stays the one place that
-/// decides these are disposable.
+/// decides these are disposable. The filter is the catalog's
+/// (`faces::people_in_use`), in the query, so the rows withheld are never
+/// read or sorted either.
 ///
 /// An empty group with a *name* still shows. That one is not debris, it is the
 /// symptom of a real failure — a named person whose faces were regrouped out
@@ -228,11 +230,8 @@ pub fn load_people(
     model_id: &str,
 ) -> Result<IdentityView, dr_catalog::CatalogError> {
     let conn = catalog.connection();
-    let people = faces::people(conn)?
+    let people = faces::people_in_use(conn)?
         .into_iter()
-        .filter(|p| {
-            p.confirmed_faces + p.suggested_faces > 0 || !p.name.trim().is_empty() || p.ignored
-        })
         .map(|p| PersonRow {
             id: p.id,
             name: p.name,
@@ -247,7 +246,7 @@ pub fn load_people(
         people,
         selected: None,
         faces: Vec::new(),
-        unassigned: faces::unassigned(conn, model_id)?.len(),
+        unassigned: faces::count_unassigned(conn, model_id)? as usize,
         calibrated: faces::calibration(conn, model_id)?.is_some_and(|(c, _)| c.valid),
     })
 }