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

Kanban/LiveStore/BoardStore.swift

@@ -196,9 +196,9 @@ public final class BoardStore {
     /// failures, and re-homes those rows here when it closes; injecting a shared center would
     /// erase precisely that distinction.
     ///
-    /// It holds only what nothing else does — one-shot write failures, the history suspension,
-    /// in-progress operations, passive signposts. The lock and the reload breakage stay this
-    /// store's own state and are composed in at render time by `bannerRows`.
+    /// It holds only what nothing else does — one-shot write failures, loss rows, the history
+    /// suspension, in-progress operations, passive signposts. The lock and the reload breakage stay
+    /// this store's own state and are composed in at render time by `bannerRows`.
     public let banners = BannerCenter()
 
     /// The rows the board window's strip renders, in precedence order.
@@ -211,6 +211,7 @@ public final class BoardStore {
             lock: readOnlyLock,
             breakage: reloadFailure,
             oneShots: banners.oneShots,
+            losses: banners.losses,
             suspension: banners.historySuspension,
             operations: banners.operations,
             signposts: banners.signposts