fix(macos): surface gateway sessions load errors

apps/macos/Sources/Clawdis/MenuContextCardInjector.swift

@@ -122,7 +122,15 @@ final class MenuContextCardInjector: NSObject, NSMenuDelegate {
             self.cacheUpdatedAt = Date()
         } catch {
             if self.cachedRows.isEmpty {
-                self.cacheErrorText = "Could not load sessions"
+                let raw = (error as? LocalizedError)?.errorDescription ?? error.localizedDescription
+                let trimmed = raw.trimmingCharacters(in: .whitespacesAndNewlines)
+                if trimmed.isEmpty {
+                    self.cacheErrorText = "Could not load sessions"
+                } else {
+                    // Keep the menu readable: one line, short.
+                    let firstLine = trimmed.split(whereSeparator: \.isNewline).first.map(String.init) ?? trimmed
+                    self.cacheErrorText = firstLine.count > 90 ? "\(firstLine.prefix(87))…" : firstLine
+                }
             }
             self.cacheUpdatedAt = Date()
         }

apps/macos/Sources/Clawdis/SessionData.swift

@@ -238,7 +238,12 @@ enum SessionLoader {
         do {
             data = try await ControlChannel.shared.request(method: "sessions.list", params: params)
         } catch {
-            throw SessionLoadError.gatewayUnavailable(error.localizedDescription)
+            let msg = (error as? LocalizedError)?.errorDescription ?? error.localizedDescription
+            if msg.localizedCaseInsensitiveContains("unknown method: sessions.list") {
+                throw SessionLoadError.gatewayUnavailable(
+                    "Gateway is too old (missing sessions.list). Restart/update the gateway.")
+            }
+            throw SessionLoadError.gatewayUnavailable(msg)
         }
 
         let decoded: GatewaySessionsListResponse