Give the macOS app a proper icon matching iOS (#1414)

The macOS Debug configuration uses AppIconDebug, which had no mac-idiom
entries at all, so Debug builds shipped with the generic dock icon. And
the mac slots in AppIcon reused the full-bleed square iOS artwork; macOS
does not mask icons at render time, so even Release showed a sharp-
cornered square.

- Regenerate all AppIcon mac PNGs with the Big Sur icon grid baked in
  (824x824 rounded-rect body on a transparent 1024 canvas + standard
  drop shadow), derived from the same 1024 iOS art.
- Add a full mac icon set to AppIconDebug from the green debug artwork.
- Add scripts/generate-mac-appicon.swift (pure CoreGraphics) to
  re-derive the mac sizes whenever the 1024 source changes.

Co-authored-by: jack <jackjackbits@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

bitchat/Assets.xcassets/AppIconDebug.appiconset/Contents.json

@@ -27,6 +27,66 @@
       "idiom" : "universal",
       "platform" : "ios",
       "size" : "1024x1024"
+    },
+    {
+      "filename" : "mac_16x16.png",
+      "idiom" : "mac",
+      "scale" : "1x",
+      "size" : "16x16"
+    },
+    {
+      "filename" : "mac_16x16@2x.png",
+      "idiom" : "mac",
+      "scale" : "2x",
+      "size" : "16x16"
+    },
+    {
+      "filename" : "mac_32x32.png",
+      "idiom" : "mac",
+      "scale" : "1x",
+      "size" : "32x32"
+    },
+    {
+      "filename" : "mac_32x32@2x.png",
+      "idiom" : "mac",
+      "scale" : "2x",
+      "size" : "32x32"
+    },
+    {
+      "filename" : "mac_128x128.png",
+      "idiom" : "mac",
+      "scale" : "1x",
+      "size" : "128x128"
+    },
+    {
+      "filename" : "mac_128x128@2x.png",
+      "idiom" : "mac",
+      "scale" : "2x",
+      "size" : "128x128"
+    },
+    {
+      "filename" : "mac_256x256.png",
+      "idiom" : "mac",
+      "scale" : "1x",
+      "size" : "256x256"
+    },
+    {
+      "filename" : "mac_256x256@2x.png",
+      "idiom" : "mac",
+      "scale" : "2x",
+      "size" : "256x256"
+    },
+    {
+      "filename" : "mac_512x512.png",
+      "idiom" : "mac",
+      "scale" : "1x",
+      "size" : "512x512"
+    },
+    {
+      "filename" : "mac_512x512@2x.png",
+      "idiom" : "mac",
+      "scale" : "2x",
+      "size" : "512x512"
     }
   ],
   "info" : {

scripts/generate-mac-appicon.swift

@@ -0,0 +1,81 @@
+#!/usr/bin/env swift
+// Generates macOS app-icon PNGs from a square 1024x1024 source image.
+//
+// macOS does not mask icons at render time the way iOS does, so the rounded
+// rectangle must be baked into the artwork. This applies Apple's Big Sur icon
+// grid: an 824x824 rounded-rect body (corner radius 185.4 @1024) centered on a
+// transparent 1024 canvas, with the standard subtle drop shadow.
+//
+// Usage: swift scripts/generate-mac-appicon.swift <source-1024.png> <output-dir> <file-prefix>
+//   e.g. swift scripts/generate-mac-appicon.swift icon_1024x1024.png bitchat/Assets.xcassets/AppIcon.appiconset icon
+
+import AppKit
+import UniformTypeIdentifiers
+
+guard CommandLine.arguments.count == 4 else {
+    FileHandle.standardError.write(Data("usage: generate-mac-appicon.swift <source.png> <outdir> <prefix>\n".utf8))
+    exit(1)
+}
+
+let sourcePath = CommandLine.arguments[1]
+let outDir = URL(fileURLWithPath: CommandLine.arguments[2], isDirectory: true)
+let prefix = CommandLine.arguments[3]
+
+guard let dataProvider = CGDataProvider(url: URL(fileURLWithPath: sourcePath) as CFURL),
+      let source = CGImage(pngDataProviderSource: dataProvider, decode: nil, shouldInterpolate: true, intent: .defaultIntent) else {
+    FileHandle.standardError.write(Data("error: could not read PNG at \(sourcePath)\n".utf8))
+    exit(1)
+}
+
+let sRGB = CGColorSpace(name: CGColorSpace.sRGB)!
+
+func render(pixels: Int) -> CGImage {
+    let ctx = CGContext(
+        data: nil, width: pixels, height: pixels,
+        bitsPerComponent: 8, bytesPerRow: 0, space: sRGB,
+        bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue
+    )!
+    let side = CGFloat(pixels)
+    let inset = side * 100.0 / 1024.0
+    let body = CGRect(x: inset, y: inset, width: side - 2 * inset, height: side - 2 * inset)
+    let radius = side * 185.4 / 1024.0
+    let path = CGPath(roundedRect: body, cornerWidth: radius, cornerHeight: radius, transform: nil)
+
+    ctx.saveGState()
+    ctx.setShadow(
+        offset: CGSize(width: 0, height: -side * 10.0 / 1024.0),
+        blur: side * 20.0 / 1024.0,
+        color: CGColor(colorSpace: sRGB, components: [0, 0, 0, 0.3])
+    )
+    ctx.addPath(path)
+    ctx.setFillColor(CGColor(colorSpace: sRGB, components: [0, 0, 0, 1])!)
+    ctx.fillPath()
+    ctx.restoreGState()
+
+    ctx.saveGState()
+    ctx.addPath(path)
+    ctx.clip()
+    ctx.interpolationQuality = .high
+    ctx.draw(source, in: body)
+    ctx.restoreGState()
+
+    return ctx.makeImage()!
+}
+
+func writePNG(_ image: CGImage, to url: URL) {
+    let dest = CGImageDestinationCreateWithURL(url as CFURL, UTType.png.identifier as CFString, 1, nil)!
+    CGImageDestinationAddImage(dest, image, nil)
+    guard CGImageDestinationFinalize(dest) else {
+        FileHandle.standardError.write(Data("error: failed to write \(url.path)\n".utf8))
+        exit(1)
+    }
+}
+
+// (point size, scale) for every mac slot in an appiconset
+let slots: [(Int, Int)] = [(16, 1), (16, 2), (32, 1), (32, 2), (128, 1), (128, 2), (256, 1), (256, 2), (512, 1), (512, 2)]
+for (points, scale) in slots {
+    let suffix = scale == 1 ? "" : "@\(scale)x"
+    let url = outDir.appendingPathComponent("\(prefix)_\(points)x\(points)\(suffix).png")
+    writePNG(render(pixels: points * scale), to: url)
+    print("wrote \(url.lastPathComponent)")
+}