build: add GhosttyVt module map to xcframework and Swift example

The xcframework now generates its own headers directory with a
GhosttyVt module map instead of reusing include/ directly, which
contains the GhosttyKit module map for the macOS app. The generated
directory copies the ghostty headers and adds a module.modulemap
that exposes ghostty/vt.h as the umbrella header.

A new swift-vt-xcframework example demonstrates consuming the
xcframework from a Swift Package. It creates a terminal, writes
VT sequences, and formats the output as plain text, verifying
the full round-trip works with swift build and swift run.

example/.gitignore

@@ -3,3 +3,4 @@ dist/
 node_modules/
 example.wasm*
 build/
+.build/

example/swift-vt-xcframework/Package.swift

@@ -0,0 +1,21 @@
+// swift-tools-version: 5.9
+import PackageDescription
+
+let package = Package(
+    name: "swift-vt-xcframework",
+    platforms: [.macOS(.v13)],
+    targets: [
+        .executableTarget(
+            name: "swift-vt-xcframework",
+            dependencies: ["GhosttyVt"],
+            path: "Sources",
+            linkerSettings: [
+                .linkedLibrary("c++"),
+            ]
+        ),
+        .binaryTarget(
+            name: "GhosttyVt",
+            path: "../../zig-out/lib/ghostty-vt.xcframework"
+        ),
+    ]
+)

example/swift-vt-xcframework/README.md

@@ -0,0 +1,23 @@
+# swift-vt-xcframework
+
+Demonstrates consuming libghostty-vt from a Swift Package using the
+pre-built XCFramework. Creates a terminal, writes VT sequences into it,
+and formats the screen contents as plain text.
+
+This example requires the XCFramework to be built first.
+
+## Building
+
+First, build the XCFramework from the repository root:
+
+```shell-session
+zig build -Demit-lib-vt
+```
+
+Then build and run the Swift package:
+
+```shell-session
+cd example/swift-vt-xcframework
+swift build
+swift run
+```

example/swift-vt-xcframework/Sources/main.swift

@@ -0,0 +1,45 @@
+import GhosttyVt
+
+// Create a terminal with a small grid
+var terminal: GhosttyTerminal?
+var opts = GhosttyTerminalOptions(
+    cols: 80,
+    rows: 24,
+    max_scrollback: 0
+)
+let result = ghostty_terminal_new(nil, &terminal, opts)
+guard result == GHOSTTY_SUCCESS, let terminal else {
+    fatalError("Failed to create terminal")
+}
+
+// Write some VT-encoded content
+let text = "Hello from \u{1b}[1mSwift\u{1b}[0m via xcframework!\r\n"
+text.withCString { ptr in
+    ghostty_terminal_vt_write(terminal, ptr, strlen(ptr))
+}
+
+// Format the terminal contents as plain text
+var fmtOpts = GhosttyFormatterTerminalOptions()
+fmtOpts.size = MemoryLayout<GhosttyFormatterTerminalOptions>.size
+fmtOpts.emit = GHOSTTY_FORMATTER_FORMAT_PLAIN
+fmtOpts.trim = true
+
+var formatter: GhosttyFormatter?
+let fmtResult = ghostty_formatter_terminal_new(nil, &formatter, terminal, fmtOpts)
+guard fmtResult == GHOSTTY_SUCCESS, let formatter else {
+    fatalError("Failed to create formatter")
+}
+
+var buf: UnsafeMutablePointer<UInt8>?
+var len: Int = 0
+let allocResult = ghostty_formatter_format_alloc(formatter, nil, &buf, &len)
+guard allocResult == GHOSTTY_SUCCESS, let buf else {
+    fatalError("Failed to format")
+}
+
+print("Plain text (\(len) bytes):")
+print(String(cString: buf))
+
+ghostty_free(nil, buf, len)
+ghostty_formatter_free(formatter)
+ghostty_terminal_free(terminal)

src/build/GhosttyLibVt.zig

@@ -342,12 +342,30 @@ pub fn xcframework(
 ) *XCFrameworkStep {
     assert(lib_vt.kind == .static);
     const b = lib_vt.step.owner;
+
+    // Generate a headers directory with a module map for Swift PM.
+    // We can't use include/ directly because it contains a module map
+    // for GhosttyKit (the macOS app library).
+    const wf = b.addWriteFiles();
+    _ = wf.addCopyDirectory(
+        b.path("include/ghostty"),
+        "ghostty",
+        .{ .include_extensions = &.{".h"} },
+    );
+    _ = wf.add("module.modulemap",
+        \\module GhosttyVt {
+        \\    umbrella header "ghostty/vt.h"
+        \\    export *
+        \\}
+        \\
+    );
+
     return XCFrameworkStep.create(b, .{
         .name = "ghostty-vt",
         .out_path = b.pathJoin(&.{ b.install_prefix, "lib/ghostty-vt.xcframework" }),
         .libraries = &.{.{
             .library = lib_vt.output,
-            .headers = b.path("include/ghostty"),
+            .headers = wf.getDirectory(),
             .dsym = null,
         }},
     });