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.

core/dr-catalog/src/faces.rs

@@ -838,6 +838,22 @@ pub fn unassigned(conn: &Connection, model_id: &str) -> Result<Vec<FaceId>, Cata
     rows.collect::<Result<_, _>>().map_err(Into::into)
 }
 
+/// How many faces have no identity yet — [`unassigned`] counted rather than
+/// listed, for a screen that only shows the number.
+pub fn count_unassigned(conn: &Connection, model_id: &str) -> Result<u64, CatalogError> {
+    let n: i64 = conn.query_row(
+        &format!(
+            "SELECT COUNT(*) FROM faces f
+              LEFT JOIN face_person fp ON fp.face_id = f.id
+              WHERE fp.face_id IS NULL AND {} = ?1",
+            embedder_sql("f.model_id")
+        ),
+        [embedder_of(model_id)],
+        |r| r.get(0),
+    )?;
+    Ok(n as u64)
+}
+
 /// One face's stored embedding, as the clustering pass consumes it.
 ///
 /// A struct rather than a tuple because it crosses a crate boundary and "the
@@ -910,17 +926,46 @@ pub fn rename_person(conn: &Connection, person: PersonId, name: &str) -> Result<
 /// Merged-away people are excluded: they exist as redirects so a sync does not
 /// resurrect them, not as entries in a list.
 pub fn people(conn: &Connection) -> Result<Vec<Person>, CatalogError> {
-    let mut q = conn.prepare(
+    people_where(conn, false)
+}
+
+/// Everyone who holds a face, carries a name, or was set aside — the people a
+/// screen has a row for.
+///
+/// The rest are the empty, unnamed groups a regrouping pass leaves behind
+/// (`prune_empty_unnamed`), and on the reference library they were 17,000 of
+/// 19,000 rows: read, counted, sorted by name and then thrown away by the
+/// caller on every redraw. Filtered here, in the query, they are never
+/// sorted. The filter is SQL's `trim`, which strips spaces and not every
+/// whitespace character, so a name that is only a tab is listed rather than
+/// hidden — the safe direction for a row the user typed something into.
+pub fn people_in_use(conn: &Connection) -> Result<Vec<Person>, CatalogError> {
+    people_where(conn, true)
+}
+
+/// [`people`], with face counts aggregated once per person *before* the join
+/// rather than grouped after it: the face table is joined to the 2,000
+/// people it names, not the 19,000 rows of the people table.
+fn people_where(conn: &Connection, in_use: bool) -> Result<Vec<Person>, CatalogError> {
+    let filter = if in_use {
+        "AND (c.person_id IS NOT NULL OR trim(p.name) <> '' OR p.ignored)"
+    } else {
+        ""
+    };
+    let mut q = conn.prepare(&format!(
         "SELECT p.id, p.uuid, p.name,
-                COALESCE(SUM(fp.confirmed = 1), 0),
-                COALESCE(SUM(fp.confirmed = 0), 0),
+                COALESCE(c.confirmed, 0),
+                COALESCE(c.suggested, 0),
                 p.ignored
            FROM people p
-           LEFT JOIN face_person fp ON fp.person_id = p.id
-          WHERE p.merged_into IS NULL
-          GROUP BY p.id
-          ORDER BY 4 DESC, 5 DESC, p.name",
-    )?;
+           LEFT JOIN (SELECT person_id,
+                             SUM(confirmed = 1) AS confirmed,
+                             SUM(confirmed = 0) AS suggested
+                        FROM face_person
+                       GROUP BY person_id) c ON c.person_id = p.id
+          WHERE p.merged_into IS NULL {filter}
+          ORDER BY 4 DESC, 5 DESC, p.name"
+    ))?;
     let rows = q.query_map([], |r| {
         Ok(Person {
             id: PersonId(r.get::<_, i64>(0)? as u64),