perf(ios): wire v2.7 perf parity — instrument iOS-only VMs + surface hydration banner + opt-in toggle

Most of the v2.7 perf work was already covered on iOS via shared
code in ScarfCore — `RichChatViewModel.loadSessionHistory` (and
its skeleton-then-hydrate path), `hydrateAssistantToolCalls`,
`fetchSkeletonMessages`, `fetchRecentToolCallSkeleton`,
`ModelPreflight.detectMismatch`, and the `RemoteSQLiteBackend`
cancellation handler all flow through to the ScarfGo chat
unchanged. `CitadelServerTransport.streamScript` already
honors `Task.isCancelled` correctly via `withThrowingTaskGroup` +
`Task.checkCancellation()`, so the SSH-cancellation-on-nav-away
chain works on iOS without the Mac-side `SSHScriptRunner` fix.

Three iOS-specific gaps closed:

* IOSCronViewModel.load + IOSMemoryViewModel.load wrapped in
  `ScarfMon.measureAsync(.diskIO, "ios.cron.load")` /
  `"ios.memory.load"` — parity with the Mac `cron.load` /
  `memory.load` events. `ios.memory.load.bytes` records the
  payload size for the loaded file.
* iOS Settings → "Chat (Scarf)" section gains a toggle bound to
  `RichChatViewModel.loadHistoricalToolResultsKey` so iOS users
  can opt into Phase 2b bulk tool-result hydration, same as the
  Mac DisplayTab. The shared key means the gate inside
  `startToolHydration` reads the right value automatically — no
  extra plumbing needed.
* iOS ChatView surfaces `isHydratingTools` as a "Loading tool
  details…" connection banner (mirrors the Mac toolbar pill
  added in v2.7 perf work). Sits between the existing
  "Thinking…" banner and the empty-view fallback so chat status
  is always honest about what the agent and Scarf are doing.

Both Mac and iOS targets build clean; all 321 ScarfCore tests
pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scarf/Scarf iOS/Chat/ChatView.swift

@@ -412,6 +412,16 @@ struct ChatView: View {
                     tint: ScarfColor.info,
                     showSpinner: true
                 )
+            } else if controller.vm.isHydratingTools {
+                // v2.7 — Phase 2 tool-call hydration is in flight.
+                // Bare conversation skeleton is already on screen;
+                // this banner tells the user the tool cards are
+                // about to fill in.
+                connectionBannerStrip(
+                    text: "Loading tool details…",
+                    tint: ScarfColor.info,
+                    showSpinner: true
+                )
             } else {
                 EmptyView()
             }

scarf/Scarf iOS/Settings/SettingsView.swift

@@ -13,6 +13,13 @@ struct SettingsView: View {
     @State private var vm: IOSSettingsViewModel
     @State private var showRawYAML = false
     @State private var editingSpec: SettingSpec?
+    /// v2.7 — Scarf-local opt-in to bulk-fetch tool result CONTENT
+    /// when resuming past chats. Default off; the shared
+    /// `RichChatViewModel` reads this same UserDefaults key on
+    /// every chat resume so iOS gets the same skeleton-then-hydrate
+    /// behavior as Mac.
+    @AppStorage(RichChatViewModel.loadHistoricalToolResultsKey)
+    private var loadHistoricalToolResults: Bool = false
 
     private static let sharedContextID: ServerID = ServerID(
         uuidString: "00000000-0000-0000-0000-0000000000A1"
@@ -164,6 +171,28 @@ struct SettingsView: View {
             yesNoRow("Inline diffs", vm.config.display.inlineDiffs)
             LabeledContent("Personality", value: vm.config.personality)
         }
+        chatScarfSection
+    }
+
+    /// v2.7 — Scarf-local chat preferences. Mirrors the Mac Settings
+    /// → Display → "Load tool results in past chats" toggle. Lives in
+    /// its own section so it's clear these are app-side settings, not
+    /// Hermes config values.
+    @ViewBuilder
+    private var chatScarfSection: some View {
+        Section {
+            Toggle(isOn: $loadHistoricalToolResults) {
+                VStack(alignment: .leading, spacing: 2) {
+                    Text("Load tool results in past chats")
+                        .font(.body)
+                    Text("Off (default) keeps past chat resumes fast on slow remotes — tool call cards still render, but the inspector lazy-loads each result when you open it.")
+                        .font(.caption)
+                        .foregroundStyle(.secondary)
+                }
+            }
+        } header: {
+            Text("Chat (Scarf)")
+        }
     }
 
     @ViewBuilder