feat: add LivelineCanvas Swift Package with native iOS canvas renderer

.github/workflows/swift-ci.yml

@@ -0,0 +1,28 @@
+name: Swift CI
+
+on:
+  push:
+    paths:
+      - 'Sources/**'
+      - 'Tests/**'
+      - 'Package.swift'
+      - '.github/workflows/swift-ci.yml'
+  pull_request:
+    paths:
+      - 'Sources/**'
+      - 'Tests/**'
+      - 'Package.swift'
+      - '.github/workflows/swift-ci.yml'
+
+jobs:
+  ios-build:
+    name: Build for iOS + test
+    runs-on: macos-15
+    steps:
+      - uses: actions/checkout@v4
+      # The UIKit renderer only compiles on iOS/macCatalyst — swift test on
+      # macOS/Linux skips it entirely, so an iOS build is the real gate.
+      - name: Build (iOS)
+        run: xcodebuild build -scheme LivelineCanvas -destination 'generic/platform=iOS'
+      - name: Unit tests (host)
+        run: swift test

.gitignore

@@ -5,3 +5,4 @@ dist/
 *.tsbuildinfo
 dev/showcase.*
 dev/multiline.*
+.build/

Package.swift

@@ -0,0 +1,27 @@
+// swift-tools-version: 5.9
+import PackageDescription
+
+let package = Package(
+    name: "LivelineCanvas",
+    platforms: [
+        .iOS(.v15),
+        .macCatalyst(.v15)
+    ],
+    products: [
+        .library(
+            name: "LivelineCanvas",
+            targets: ["LivelineCanvas"]
+        )
+    ],
+    targets: [
+        .target(
+            name: "LivelineCanvas",
+            path: "Sources/LivelineCanvas"
+        ),
+        .testTarget(
+            name: "LivelineCanvasTests",
+            dependencies: ["LivelineCanvas"],
+            path: "Tests/LivelineCanvasTests"
+        )
+    ]
+)