P3.1: iOS goldens @2x + PNG optimizer + Makefile record/verify targets

- SnapshotGalleryTests rendered at displayScale: 2.0 (was native 3.0)
  → 49MB → 15MB (~69% reduction)
- Records via SNAPSHOT_TESTING_RECORD=1 env var (no code edits needed)
- scripts/optimize_goldens.sh runs zopflipng (or pngcrush fallback)
  over both iOS and Android golden dirs
- scripts/{record,verify}_snapshots.sh one-command wrappers
- Makefile targets: make {record,verify,optimize}-snapshots

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

iosApp/HoneyDueTests/SnapshotGalleryTests.swift

@@ -25,9 +25,26 @@
 //
 //  Recording goldens
 //  -----------------
-//  Set `isRecording = true` in `setUp()`, run the target, then flip back to
-//  `false` before committing. CI fails the build if a screen diverges from
-//  its golden by more than the precision threshold.
+//  Preferred: `make record-snapshots` (or `./scripts/record_snapshots.sh
+//  --ios-only`). The script exports `SNAPSHOT_TESTING_RECORD=1` in the
+//  xcodebuild env, deletes the old `__Snapshots__/SnapshotGalleryTests`
+//  directory, runs the target, then invokes the shared PNG optimizer.
+//
+//  Manual override: set the `SNAPSHOT_TESTING_RECORD` env var to `1` in
+//  the Xcode scheme's Test action (Edit Scheme → Test → Arguments →
+//  Environment Variables) and re-run the test target. CI fails the
+//  build if a screen diverges from its golden by more than the
+//  precision threshold.
+//
+//  Rendering scale
+//  ---------------
+//  We force `displayScale: 2.0` on every snapshot. The iPhone 15 /
+//  iPhone 13 simulators default to the device's native 3x, which on a
+//  full-screen gradient-heavy SwiftUI view produced 800–1000 KB PNGs
+//  per image. @2x halves the linear dimensions (2.25x fewer pixels) and
+//  is still plenty to catch layout regressions. Combined with
+//  `scripts/optimize_goldens.sh` (zopflipng / pngcrush) this keeps us
+//  under the 150 KB per-image budget enforced by CI.
 //
 
 @preconcurrency import SnapshotTesting
@@ -39,8 +56,14 @@ import ComposeApp
 @MainActor
 final class SnapshotGalleryTests: XCTestCase {
 
-    // Flip to true locally, run the scheme, revert, commit.
-    private static let recordMode: SnapshotTestingConfiguration.Record = .missing
+    // Record mode is driven by the `SNAPSHOT_TESTING_RECORD` env var so
+    // `scripts/record_snapshots.sh` can flip it without mutating this file.
+    // When the var is unset/empty we only write missing goldens (`.missing`)
+    // so local dev runs never silently overwrite committed PNGs.
+    private static var recordMode: SnapshotTestingConfiguration.Record {
+        let env = ProcessInfo.processInfo.environment["SNAPSHOT_TESTING_RECORD"] ?? ""
+        return (env == "1" || env.lowercased() == "true") ? .all : .missing
+    }
 
     override func invokeTest() {
         withSnapshotTesting(record: Self.recordMode) {
@@ -63,6 +86,12 @@ final class SnapshotGalleryTests: XCTestCase {
     private static let pixelPrecision: Float = 0.97
     private static let perceptualPrecision: Float = 0.95
 
+    /// Force @2x rendering regardless of the simulator device's native
+    /// `displayScale`. See the class-level "Rendering scale" comment for
+    /// rationale. 2.0 keeps PNGs under the size budget without sacrificing
+    /// the structural detail our parity gallery cares about.
+    private static let forcedDisplayScale: CGFloat = 2.0
+
     private func snap<V: View>(
         _ name: String,
         file: StaticString = #filePath,
@@ -80,7 +109,10 @@ final class SnapshotGalleryTests: XCTestCase {
                 precision: Self.pixelPrecision,
                 perceptualPrecision: Self.perceptualPrecision,
                 layout: .device(config: .iPhone13),
-                traits: .init(userInterfaceStyle: .light)
+                traits: .init(traitsFrom: [
+                    UITraitCollection(userInterfaceStyle: .light),
+                    UITraitCollection(displayScale: Self.forcedDisplayScale),
+                ])
             ),
             named: "\(name)_light",
             file: file,
@@ -93,7 +125,10 @@ final class SnapshotGalleryTests: XCTestCase {
                 precision: Self.pixelPrecision,
                 perceptualPrecision: Self.perceptualPrecision,
                 layout: .device(config: .iPhone13),
-                traits: .init(userInterfaceStyle: .dark)
+                traits: .init(traitsFrom: [
+                    UITraitCollection(userInterfaceStyle: .dark),
+                    UITraitCollection(displayScale: Self.forcedDisplayScale),
+                ])
             ),
             named: "\(name)_dark",
             file: file,