feat(SaveSystem): third-party emulator detection & migration guide

- Add KnownEmulator enum to PVPrimitives with detection via canOpenURL
- Add ExternalEmulatorMigrationView with per-emulator step-by-step guides
  for Delta, RetroArch, Manic Emu, PPSSPP, and Gamma
- Wire view into Settings → Library section
- Add delta/retroarch/ppsspp to LSApplicationQueriesSchemes in all
  iOS and tvOS Info.plist variants
- Add whats-new.json entry for 3.9.2
- Add .changelog/3556.md fragment

Part of #3551

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: github-actions[bot]

.changelog/3556.md

@@ -0,0 +1,5 @@
+### Added
+- **Third-Party Emulator Migration Guide** — New "Import from Another Emulator" screen in Settings → Library detects installed emulators (Delta, RetroArch, Manic Emu, PPSSPP, Gamma) and provides step-by-step export/import instructions for each.
+- **`KnownEmulator` enum** — `PVPrimitives` now exposes a `KnownEmulator` enum with metadata (bundle ID, URL scheme, save extensions, system summary) for each supported third-party emulator and a `@MainActor` detection helper using `canOpenURL`.
+- **`LSApplicationQueriesSchemes` additions** — All iOS and tvOS Info.plist variants now declare the `delta`, `retroarch`, and `ppsspp` URL schemes so presence detection works at runtime.
+- **Manual Import Guide** — Covers `.sav`/`.srm`/`.state` imports via Files.app and Provenance's built-in web server for users not migrating from a specific third-party app.

PVPrimitives/Sources/PVPrimitives/KnownEmulator.swift

@@ -0,0 +1,137 @@
+//
+//  KnownEmulator.swift
+//  PVPrimitives
+//
+//  Created by Joseph Mattiello on 3/28/26.
+//  Copyright © 2026 Provenance Emu. All rights reserved.
+//
+
+import Foundation
+
+/// A known third-party emulator that may be installed on the user's device.
+///
+/// iOS sandboxing prevents direct file access to other apps' containers, but
+/// we can probe for their presence via URL schemes and guide users through
+/// manual export/import workflows.
+public enum KnownEmulator: String, CaseIterable, Sendable {
+    /// Delta — Nintendo multi-system emulator by Riley Testut.
+    /// Supports NES, SNES, N64, GBA, GBC, DS.
+    case delta
+
+    /// Manic Emu — GBA, NES, SNES, and Sega Genesis emulator.
+    case manic
+
+    /// RetroArch — multi-system emulator frontend with a large core library.
+    case retroArch
+
+    /// PPSSPP — PSP emulator.
+    case ppsspp
+
+    /// Gamma — Game Boy / Game Boy Color emulator.
+    case gamma
+}
+
+// MARK: - Display properties
+
+public extension KnownEmulator {
+    /// Human-readable name of the emulator.
+    var displayName: String {
+        switch self {
+        case .delta:     return "Delta"
+        case .manic:     return "Manic Emu"
+        case .retroArch: return "RetroArch"
+        case .ppsspp:    return "PPSSPP"
+        case .gamma:     return "Gamma"
+        }
+    }
+
+    /// Bundle identifier of the emulator app.
+    var bundleIdentifier: String {
+        switch self {
+        case .delta:     return "com.rileytestut.Delta"
+        case .manic:     return "com.manticstudios.ManticEmu"
+        case .retroArch: return "com.libretro.RetroArch"
+        case .ppsspp:    return "org.ppsspp.ppsspp"
+        case .gamma:     return "com.littleredgames.GambatteGB"
+        }
+    }
+
+    /// URL scheme used to probe whether the app is installed.
+    /// `nil` if the emulator has no registered URL scheme.
+    var urlScheme: String? {
+        switch self {
+        case .delta:     return "delta"
+        case .manic:     return nil
+        case .retroArch: return "retroarch"
+        case .ppsspp:    return "ppsspp"
+        case .gamma:     return nil
+        }
+    }
+
+    /// SF Symbol name that best represents this emulator's primary platform(s).
+    var symbolName: String {
+        switch self {
+        case .delta:     return "gamecontroller.fill"
+        case .manic:     return "bolt.fill"
+        case .retroArch: return "cpu.fill"
+        case .ppsspp:    return "memorychip"
+        case .gamma:     return "squareshape.dotted.squareshape"
+        }
+    }
+
+    /// Short description of which systems/games this emulator handles.
+    var systemSummary: String {
+        switch self {
+        case .delta:     return "NES, SNES, N64, GBA, GBC, DS"
+        case .manic:     return "GBA, NES, SNES, Genesis"
+        case .retroArch: return "60+ systems"
+        case .ppsspp:    return "PlayStation Portable (PSP)"
+        case .gamma:     return "Game Boy, Game Boy Color"
+        }
+    }
+
+    /// The save-file extension(s) this emulator primarily uses.
+    var saveExtensions: [String] {
+        switch self {
+        case .delta:     return ["sav", "ssv"]
+        case .manic:     return ["sav", "srm"]
+        case .retroArch: return ["sav", "srm", "state"]
+        case .ppsspp:    return ["ppst"]
+        case .gamma:     return ["sav"]
+        }
+    }
+}
+
+// MARK: - Detection
+
+public extension KnownEmulator {
+    /// Returns `true` when the emulator appears to be installed.
+    ///
+    /// Detection is performed via `UIApplication.canOpenURL(_:)`, which requires
+    /// the scheme to be listed in `LSApplicationQueriesSchemes` inside Info.plist.
+    /// On tvOS and simulator builds this always returns `false`.
+    @MainActor
+    var isInstalled: Bool {
+        #if os(iOS) && !targetEnvironment(simulator)
+        guard let scheme = urlScheme,
+              let url = URL(string: "\(scheme)://") else {
+            return false
+        }
+        // UIApplication is only available when imported via UIKit
+        // We use dynamic lookup to avoid a hard UIKit import in PVPrimitives.
+        guard let application = NSClassFromString("UIApplication"),
+              let shared = application.value(forKeyPath: "sharedApplication") as? NSObject else {
+            return false
+        }
+        return (shared.perform(NSSelectorFromString("canOpenURL:"), with: url)?.takeUnretainedValue() as? Bool) ?? false
+        #else
+        return false
+        #endif
+    }
+
+    /// Returns all emulators that are detected as installed on the current device.
+    @MainActor
+    static var installedEmulators: [KnownEmulator] {
+        KnownEmulator.allCases.filter { $0.isInstalled }
+    }
+}

PVUI/Sources/PVSwiftUI/Resources/whats-new.json

@@ -688,5 +688,29 @@
         "subtitle": "The ra.me relay is pre-filled out of the box so online play works without any manual setup on a fresh install."
       }
     ]
+  },
+  {
+    "version": "3.9.2",
+    "title": "Save Migration Guide",
+    "features": [
+      {
+        "symbolName": "arrow.triangle.2.circlepath",
+        "symbolColor": "blue",
+        "title": "Import from Other Emulators",
+        "subtitle": "New step-by-step guide to migrate your saves from Delta, RetroArch, Manic Emu, PPSSPP, and Gamma. Find it in Settings → Library."
+      },
+      {
+        "symbolName": "checkmark.circle.fill",
+        "symbolColor": "green",
+        "title": "Automatic Detection",
+        "subtitle": "Provenance now detects which emulators are installed and surfaces tailored export instructions for each one."
+      },
+      {
+        "symbolName": "folder.badge.plus",
+        "symbolColor": "purple",
+        "title": "Manual Import Guide",
+        "subtitle": "Not migrating from a specific app? A general guide covers .sav/.srm/.state imports via Files.app and the built-in web server."
+      }
+    ]
   }
 ]

PVUI/Sources/PVSwiftUI/Settings/SettingsSwiftUI.swift

@@ -2451,6 +2451,15 @@ private struct LibrarySection: View {
             #if os(tvOS)
             .retroFocusButtonStyle(showBorder: false)
             #endif
+
+            NavigationLink(destination: ExternalEmulatorMigrationView()) {
+                SettingsRow(title: "Import from Another Emulator",
+                            subtitle: "Step-by-step guide to migrate saves from Delta, RetroArch, Manic, PPSSPP, or Gamma.",
+                            icon: .sfSymbol("arrow.triangle.2.circlepath"))
+            }
+            #if os(tvOS)
+            .retroFocusButtonStyle(showBorder: false)
+            #endif
         }
     }
 }