guard: preflight leaves deferredScreens - its mockup is gone

The owner dropped preflight as a page of its own on 2026-10-13
(docs/roadmap.md § Dropped: "preflight as a page of its own (dropped
2026-10-13)"), and on 2026-10-18 said to clear what was left of it ("Чисти
этот хвост"). The mockup and its outlines.json key went in 2c23f4c; this
entry exempted a screen that no longer exists. A guard edit on the owner's
decision, alone in its commit.

go test ./internal/web/...: ok.

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

internal/web/view/guard_panel_test.go

@@ -49,7 +49,6 @@ var deferredScreens = map[string]string{
 	"in-queue":              "queue as a table / inbound queue, undecided",
 	"in-quarantine":         "inbound-quarantine, candidate",
 	"in-quarantine-message": "inbound-quarantine, candidate",
-	"preflight":             "preflight, candidate",
 }
 
 // Pages whose 2.0 content is deliberately not the mockup's (decided