fix(ios-rootmodel): surface store failures (A.3 + A.4 bundled)

Bundled because the fixes are coherent — they all add the same
mechanism (`lastError` + `os.Logger`) to the same model.

A.3 — Distinguish "no servers" from "Keychain unreachable":
- `RootModel.connect(to:)` previously used `try?` on `keyStore.load(for:)`.
  A biometric cancel or device-locked Keychain read returned nil → the
  app dropped the user into fresh onboarding, destroying the existing
  server's host/user/port. Now we catch the throw, log via os.Logger,
  set `lastError`, and stay on `.serverList`. The user sees a banner +
  Dismiss button instead of being kicked back to onboarding.
- `RootModel.load()` now logs the corrupted-blob path via os.Logger and
  sets `lastError` before falling through to onboarding (recovery is
  necessary, but the user gets context now).

A.4 — Surface delete failures in `forget()` and `disconnect()`:
- Both used `try?` on every store delete. On partial failure the
  in-memory dict was wiped while orphan Keychain entries lingered.
  Now each delete is `do/catch` with logging, failures collected into
  `lastError`. The in-memory state is reloaded from disk so it tracks
  what's actually persisted (covers the partial-failure case).

ServerListView gains an inline error banner above the list that reads
`model.lastError`, with a Dismiss button calling `clearLastError()`.

Verified: iOS build succeeds.

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

scarf/Scarf iOS/App/ScarfIOSApp.swift

@@ -1,6 +1,7 @@
 import SwiftUI
 import ScarfCore
 import ScarfIOS
+import os
 
 /// App entry point. Renders a single `WindowGroup` whose root decides
 /// between onboarding and the connected-app surface based on whether
@@ -116,19 +117,37 @@ final class RootModel {
     /// having to re-query stores on every re-render.
     private(set) var servers: [ServerID: IOSServerConfig] = [:]
 
+    /// Most recent non-fatal failure surfaced from RootModel operations
+    /// (load, connect, forget). The ServerListView renders a banner above
+    /// the list when this is non-nil with a Retry/Dismiss affordance.
+    /// `nil` after a successful op so stale errors don't linger.
+    var lastError: String?
+
     private let keyStore: any SSHKeyStore
     private let configStore: any IOSServerConfigStore
 
+    private static let logger = Logger(
+        subsystem: "com.scarf.ios",
+        category: "RootModel"
+    )
+
     init(keyStore: any SSHKeyStore, configStore: any IOSServerConfigStore) {
         self.keyStore = keyStore
         self.configStore = configStore
     }
 
+    /// Clear the surfaced error. Called by the ServerListView banner's
+    /// Dismiss button.
+    func clearLastError() {
+        lastError = nil
+    }
+
     /// Load configured servers from disk and pick an initial state.
     func load() async {
         do {
             let all = try await configStore.listAll()
             servers = all
+            lastError = nil
             if all.isEmpty {
                 // Fresh install or user forgot every server → go
                 // straight to onboarding with a new ID reserved so
@@ -138,7 +157,14 @@ final class RootModel {
                 state = .serverList
             }
         } catch {
+            // configStore is UserDefaults-backed; failures here are
+            // exceptional (corrupted v2 blob, JSONDecoder error). Surface
+            // the error to the user but recover into onboarding so they
+            // aren't permanently locked out of the app — the state is
+            // unsalvageable, the user needs to re-onboard anyway.
+            Self.logger.error("RootModel.load failed: \(error.localizedDescription, privacy: .public)")
             servers = [:]
+            lastError = "Couldn't load saved servers (\(error.localizedDescription)). Starting fresh."
             state = .onboarding(forNewServer: ServerID())
         }
     }
@@ -179,18 +205,33 @@ final class RootModel {
     /// Tap a server row → connect. Loads fresh from disk to catch any
     /// edits made through the Mac app (or future multi-device scenarios).
     func connect(to id: ServerID) async {
-        var diskConfig: IOSServerConfig? = servers[id]
-        if diskConfig == nil {
-            diskConfig = try? await configStore.load(id: id)
+        do {
+            var diskConfig: IOSServerConfig? = servers[id]
+            if diskConfig == nil {
+                diskConfig = try await configStore.load(id: id)
+            }
+            let diskKey: SSHKeyBundle? = try await keyStore.load(for: id)
+            guard let config = diskConfig, let key = diskKey else {
+                // Genuine "no row" / "no key" — preserve the pre-A.3
+                // behaviour: re-onboard under this ID so the user keeps
+                // host/user/port and just regenerates the key.
+                state = .onboarding(forNewServer: id)
+                return
+            }
+            lastError = nil
+            state = .connected(id, config, key)
+        } catch {
+            // Transient Keychain errors (biometric cancel, device
+            // locked, OS-level Keychain corruption) used to drop the
+            // user into fresh onboarding — destroying useful state.
+            // Now we keep them on the server list with a banner so
+            // they can retry once the Keychain is reachable again.
+            Self.logger.error(
+                "RootModel.connect failed for \(id, privacy: .public): \(error.localizedDescription, privacy: .public)"
+            )
+            lastError = "Couldn't unlock server credentials: \(error.localizedDescription)"
+            state = .serverList
         }
-        let diskKey: SSHKeyBundle? = try? await keyStore.load(for: id)
-        guard let config = diskConfig, let key = diskKey else {
-            // Missing key → force re-onboarding under this ID so the
-            // user can regenerate without losing host/user/port.
-            state = .onboarding(forNewServer: id)
-            return
-        }
-        state = .connected(id, config, key)
     }
 
     /// Soft disconnect: return to the server list without wiping
@@ -211,20 +252,60 @@ final class RootModel {
 
     /// Hard forget: wipe the specified server's key + config, refresh
     /// the list, transition to serverList (or onboarding if empty).
+    /// Per-store failures are captured in `lastError` so a partial
+    /// forget surfaces a banner instead of silently leaving orphans.
     func forget(id: ServerID) async {
-        try? await keyStore.delete(for: id)
-        try? await configStore.delete(id: id)
+        var failures: [String] = []
+        do {
+            try await keyStore.delete(for: id)
+        } catch {
+            Self.logger.error(
+                "RootModel.forget keyStore.delete failed for \(id, privacy: .public): \(error.localizedDescription, privacy: .public)"
+            )
+            failures.append("Keychain: \(error.localizedDescription)")
+        }
+        do {
+            try await configStore.delete(id: id)
+        } catch {
+            Self.logger.error(
+                "RootModel.forget configStore.delete failed for \(id, privacy: .public): \(error.localizedDescription, privacy: .public)"
+            )
+            failures.append("Config: \(error.localizedDescription)")
+        }
+        // Reload from disk so in-memory state reflects what's actually
+        // persisted — covers the partial-failure case where Keychain
+        // succeeded but config didn't (or vice versa).
         servers = (try? await configStore.listAll()) ?? [:]
+        if failures.isEmpty {
+            lastError = nil
+        } else {
+            lastError = "Couldn't fully forget server: " + failures.joined(separator: "; ")
+        }
         state = servers.isEmpty ? .onboarding(forNewServer: ServerID()) : .serverList
     }
 
     /// Legacy v1 "Disconnect" that wipes EVERYTHING. Kept for back-compat
     /// with any caller that still hits the no-arg path (there shouldn't
     /// be any after 3.5 lands, but the protocol still supports it).
+    /// Same partial-failure semantics as `forget(id:)`.
     func disconnect() async {
-        try? await keyStore.delete()
-        try? await configStore.delete()
-        servers = [:]
+        var failures: [String] = []
+        do {
+            try await keyStore.delete()
+        } catch {
+            Self.logger.error("RootModel.disconnect keyStore.delete failed: \(error.localizedDescription, privacy: .public)")
+            failures.append("Keychain: \(error.localizedDescription)")
+        }
+        do {
+            try await configStore.delete()
+        } catch {
+            Self.logger.error("RootModel.disconnect configStore.delete failed: \(error.localizedDescription, privacy: .public)")
+            failures.append("Config: \(error.localizedDescription)")
+        }
+        servers = (try? await configStore.listAll()) ?? [:]
+        if !failures.isEmpty {
+            lastError = "Couldn't fully sign out: " + failures.joined(separator: "; ")
+        }
         state = .onboarding(forNewServer: ServerID())
     }
 }

scarf/Scarf iOS/Servers/ServerListView.swift

@@ -19,6 +19,26 @@ struct ServerListView: View {
     var body: some View {
         NavigationStack {
             List {
+                if let err = model.lastError {
+                    Section {
+                        VStack(alignment: .leading, spacing: 8) {
+                            Label("Something went wrong", systemImage: "exclamationmark.triangle.fill")
+                                .foregroundStyle(.orange)
+                                .font(.headline)
+                            Text(err)
+                                .font(.callout)
+                                .foregroundStyle(.secondary)
+                                .fixedSize(horizontal: false, vertical: true)
+                            HStack(spacing: 12) {
+                                Button("Dismiss") { model.clearLastError() }
+                                    .buttonStyle(.bordered)
+                                    .controlSize(.small)
+                            }
+                        }
+                        .padding(.vertical, 4)
+                    }
+                }
+
                 Section {
                     ForEach(sortedServers, id: \.id) { row in
                         ServerListRow(row: row) {