feat(panel-snapshot): add five offscreen panels for update states

Render panels 10-14 showing the update check states:
- panel-10-update-idle: menu with 3 captures, no update available
- panel-11-update-checking: same as 10, but row reads "Checking..."
- panel-12-update-uptodate: footer status shows "Redline X.Y.Z is up to date, checked 10:42 Dubai"
- panel-13-update-staged: row "Update to 9.9.9" present, footer status "Update to 9.9.9 is ready"
- panel-14-update-revert: row "Revert to 0.2.0" present

All five panels driven by model state only; never touch real appcast or UserDefaults.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012ZiTXPbPCSjzPVsfoweAbp

Sources/Shotdeck/PanelSnapshot.swift

@@ -155,6 +155,37 @@ enum PanelSnapshot {
         model.replaceRegion(sampleRegion())
         try await addSampleCaptures(to: model)
         try renderMenuBar(model: model, to: directory, name: "09-captures-present-onedrive")
+
+        // 10 — update idle: 3 captures, no update available, footer "Redline <ver>", row "Check for updates".
+        let (updateModel, updateRoot) = try makeIsolatedModel()
+        defer { try? FileManager.default.removeItem(at: updateRoot) }
+        updateModel.snapshotSetScreenRecordingGranted(true)
+        updateModel.replaceRegion(sampleRegion())
+        try await addSampleCaptures(to: updateModel)
+        // No update set, updateChecker in idle state, no previous version
+        updateModel.snapshotSetPreviousVersion(nil)
+        try renderMenuBar(model: updateModel, to: directory, name: "10-update-idle")
+
+        // 11 — update checking: same as 10 but isCheckingForUpdates = true.
+        updateModel.snapshotSetIsCheckingForUpdates(true)
+        try renderMenuBar(model: updateModel, to: directory, name: "11-update-checking")
+        updateModel.snapshotSetIsCheckingForUpdates(false)
+
+        // 12 — update up-to-date: footer status line reads "Redline <ver> is up to date, checked 10:42 Dubai".
+        let upToDateMessage = "Redline \(updateModel.appVersion) is up to date, checked 10:42 Dubai"
+        updateModel.snapshotSetUpdateStatusMessage(upToDateMessage)
+        try renderMenuBar(model: updateModel, to: directory, name: "12-update-uptodate")
+
+        // 13 — update staged: row "Update to 9.9.9" present, footer status "Update to 9.9.9 is ready".
+        updateModel.snapshotSetUpdateAvailable(version: "9.9.9", notes: "Test release")
+        updateModel.snapshotSetUpdateStatusMessage("Update to 9.9.9 is ready")
+        try renderMenuBar(model: updateModel, to: directory, name: "13-update-staged")
+
+        // 14 — update revert: row "Revert to 0.2.0" present.
+        updateModel.snapshotSetUpdateAvailable(version: nil, notes: nil)  // Clear the staged update
+        updateModel.snapshotSetUpdateStatusMessage(nil)
+        updateModel.snapshotSetPreviousVersion("0.2.0")
+        try renderMenuBar(model: updateModel, to: directory, name: "14-update-revert")
     }
 
     @MainActor
@@ -360,6 +391,40 @@ extension AppModel {
         )
         self[keyPath: writable] = granted
     }
+
+    /// Snapshot-only: set isCheckingForUpdates without triggering a real check.
+    func snapshotSetIsCheckingForUpdates(_ checking: Bool) {
+        let writable: ReferenceWritableKeyPath<AppModel, Bool> = unsafeBitCast(
+            \AppModel.isCheckingForUpdates, to: ReferenceWritableKeyPath<AppModel, Bool>.self
+        )
+        self[keyPath: writable] = checking
+    }
+
+    /// Snapshot-only: set updateStatusMessage (statusLine alias) for panel display.
+    func snapshotSetUpdateStatusMessage(_ message: String?) {
+        setStatus(message)
+    }
+
+    /// Snapshot-only: set updateAvailable without triggering a real download.
+    func snapshotSetUpdateAvailable(version: String?, notes: String?) {
+        if let version = version, let notes = notes {
+            let writable: ReferenceWritableKeyPath<AppModel, (version: String, notes: String)?> = unsafeBitCast(
+                \AppModel.updateAvailable, to: ReferenceWritableKeyPath<AppModel, (version: String, notes: String)?>.self
+            )
+            self[keyPath: writable] = (version: version, notes: notes)
+        } else {
+            let writable: ReferenceWritableKeyPath<AppModel, (version: String, notes: String)?> = unsafeBitCast(
+                \AppModel.updateAvailable, to: ReferenceWritableKeyPath<AppModel, (version: String, notes: String)?>.self
+            )
+            self[keyPath: writable] = nil
+        }
+    }
+
+    /// Snapshot-only: set a fake previousVersion for the revert panel.
+    func snapshotSetPreviousVersion(_ version: String?) {
+        updateChecker.snapshotPreviousVersionOverride = version
+        updateChecker.snapshotUsesPreviousVersionOverride = true
+    }
 }
 
 private enum SnapshotError: Error, CustomStringConvertible {