Expose the Supply run title job and cover the replacement race

POST /shopping/{weekStart}/generate now answers with title_job_id, and
Push to Calendar's supply_run carries it too, so a client can follow the
title_supply_run job through GET /jobs/{id}, including a title_failed
failure. It is null when the list already has its title or was not
generated.

Add a regression test that replaces the week's list after archive_title
answers but before the title is stored: the old job fails title_failed
and the replacement stays untitled.

Maestro task a55adc28-4d8b-4517-b1d7-dcff39ea5a09.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/shopping/title_test.go

@@ -311,3 +311,38 @@ func TestGenerateTitleOverlapAcrossRename(t *testing.T) {
 		t.Errorf("stored title = %v, want one of the two titles", deref(got))
 	}
 }
+
+// TestGenerateTitleNotStoredOnReplacedList: a list replaced by a new
+// untitled list of the same week once archive_title has answered, before
+// its title is stored, keeps the replacement untitled; the old list's
+// title job fails, and the failure is logged.
+func TestGenerateTitleNotStoredOnReplacedList(t *testing.T) {
+	e := titleWeek(t)
+	e.model.QueueGenerate(titled("Noodles, Tacos and Chili"))
+	e.afterTitle = func() {
+		for _, stmt := range []string{
+			`DELETE FROM shopping_items WHERE group_id IN (SELECT id FROM shopping_groups WHERE list_id IN (SELECT id FROM shopping_lists WHERE week_start = ?1))`,
+			`DELETE FROM shopping_groups WHERE list_id IN (SELECT id FROM shopping_lists WHERE week_start = ?1)`,
+			`UPDATE shopping_lists SET id = 'replacement' WHERE week_start = ?1`,
+		} {
+			if _, err := e.st.Writer.Exec(stmt, week.String()); err != nil {
+				t.Error(err)
+			}
+		}
+	}
+
+	g := e.generate(t)
+	wantJob(t, e.waitTitle(t, g), jobs.StatusFailed, shopping.ReasonTitleFailed)
+
+	var id string
+	if err := e.st.Reader.QueryRow(`SELECT id FROM shopping_lists WHERE week_start = ?`, week.String()).Scan(&id); err != nil {
+		t.Fatal(err)
+	}
+	if id != "replacement" || id == g.List.ID {
+		t.Fatalf("week's list = %s, want the replacement of %s", id, g.List.ID)
+	}
+	wantUntitled(t, "replacement's title", e.storedTitle(t))
+	if !strings.Contains(e.log.String(), "the Supply run was frozen or replaced before its title was stored") {
+		t.Errorf("log lacks the failure:\n%s", e.log.String())
+	}
+}