linetest: a test on request for a box that seeds all day (R-1250)

GET /host/line-test reports waiting_for_quiet (due, in the window, tunnel up, only the quiet
missing); POST /host/line-test/run runs one measurement with a 5 s settle and a 10 s quiet
check instead of 10 quiet minutes, runs 5 s apart (~55 s). Every other weekly rule holds.
Commit only; the release rides the next train.

cmd/felhom-agent/linetest_wiring_test.go

@@ -5,8 +5,16 @@ import (
 	"go/parser"
 	"go/token"
 	"testing"
+
+	"gitea.dooplex.hu/admin/felhom-agent/internal/linetest"
+	"gitea.dooplex.hu/admin/felhom-agent/internal/localapi"
 )
 
+// R-1250: SetLineTest takes a LineTestReader and finds the request half by a type assertion, so a Tester that lost
+// WaitingForQuiet or RunNow would compile and silently answer 503 to every seeding box. This line makes it a build
+// failure instead.
+var _ localapi.LineTestRequester = (*linetest.Tester)(nil)
+
 // R-1247: the weekly line test has the fstrim shape (component + reporter seam + goroutine) plus a local-API reader,
 // so its wiring is asserted from the AST. It must share the ONE heavy-op gate (heavyOps) — or it could run beside a
 // backup — and take its server from the tunnel manager, never a literal address.