Add the loss-row banner class and retone degraded paste

02 ratified a warning-tone class for non-failure losses — content that
didn't arrive though nothing failed: a degraded paste, folders skipped
from a Finder drop, their future kin. Loss rows take the one-shot's
dismissable-untimed lifecycle (a loss the user didn't notice is the
harm) and rank below the true failures, above commit and attachment
notices. BannerCenter grows LossBanner, postLoss, and the
skipped-folders phrasing; the degraded-paste notice moves off its
signpost onto the new class, ending its too-quiet ranking.

Claude-Session: https://claude.ai/code/session_01SR4XGjmBE16ZUYWpfFHXwY

KanbanTests/ClipboardTests.swift

@@ -764,6 +764,29 @@ struct DegradedPasteBannerTests {
     func postingNothing() {
         let center = BannerCenter()
         center.postDegradedPaste([])
+        #expect(center.losses.isEmpty)
         #expect(center.signposts.isEmpty)
     }
+
+    @Test("A degraded paste lands in the loss class, not the signpost class")
+    @MainActor
+    func postingLandsAsALossRow() {
+        // Settled 2026-07-28 (DESIGN/02-architecture.md § The banner surface, "Loss rows"): the
+        // degraded paste retoned from a signpost onto the new warning-tone loss class — content
+        // that didn't arrive though nothing failed, ranking below the true failures and above the
+        // ambient notices rather than at the bottom of the strip.
+        let center = BannerCenter()
+        center.postDegradedPaste([.init(title: "Fix login", attachments: 3)])
+
+        #expect(center.losses.count == 1)
+        #expect(center.losses.first?.message == "Pasted 'Fix login' without its 3 attachments")
+        #expect(center.signposts.isEmpty, "the degraded paste no longer posts a signpost")
+
+        let rows = BannerCenter.rows(
+            lock: nil, breakage: nil, oneShots: [], losses: center.losses, suspension: nil, operations: []
+        )
+        #expect(rows.count == 1)
+        #expect(rows[0].tone == .warning)
+        #expect(rows[0].dismissID == center.losses.first?.id)
+    }
 }