fix: Linux compatibility for Terminal, SignalManager, and AppStorage

- Replace #if os(Linux) with #if canImport(Glibc/Musl/Darwin) import guards
- Add TermFlag typealias to fix termios flag width mismatch (UInt vs UInt32)
- Add platform import guard to SignalManager for POSIX signal visibility
- Replace DispatchQueue.global with Task.detached in AppStorage
- Add XDG_CONFIG_HOME fallback for config directory resolution
- Add Linux Build & Test CI job (swift:6.0 container on ubuntu-latest)

.github/workflows/ci.yml

@@ -30,6 +30,21 @@ jobs:
       - name: Run SwiftLint
         run: swiftlint
 
+  linux-build:
+    name: Linux Build & Test
+    runs-on: ubuntu-latest
+    container:
+      image: swift:6.0
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Build
+        run: swift build
+
+      - name: Test
+        run: swift test
+
   build-docs:
     name: Build DocC
     needs: lint

Sources/TUIKit/App/SignalManager.swift

@@ -7,6 +7,14 @@
 
 import Foundation
 
+#if canImport(Glibc)
+    import Glibc
+#elseif canImport(Musl)
+    import Musl
+#elseif canImport(Darwin)
+    import Darwin
+#endif
+
 // MARK: - Signal Flags
 
 /// Flag set by the SIGWINCH signal handler to request a re-render.

Sources/TUIKit/Core/AppStorage.swift

@@ -24,12 +24,36 @@ public protocol StorageBackend: Sendable {
     func synchronize()
 }
 
+// MARK: - Config Directory
+
+/// Returns the app-specific configuration directory.
+///
+/// Resolves the directory in this order:
+/// 1. `$XDG_CONFIG_HOME/<appName>` (Linux convention)
+/// 2. `~/.config/<appName>` (fallback)
+///
+/// This ensures correct behavior on Linux where `$XDG_CONFIG_HOME`
+/// may differ from `~/.config`.
+private func appConfigDirectory() -> URL {
+    let appName = ProcessInfo.processInfo.processName
+
+    if let xdgConfig = ProcessInfo.processInfo.environment["XDG_CONFIG_HOME"], !xdgConfig.isEmpty {
+        return URL(fileURLWithPath: xdgConfig)
+            .appendingPathComponent(appName)
+    }
+
+    return FileManager.default.homeDirectoryForCurrentUser
+        .appendingPathComponent(".config")
+        .appendingPathComponent(appName)
+}
+
 // MARK: - JSON File Storage
 
 /// A storage backend that persists data to a JSON file.
 ///
 /// This is the default storage backend for TUIKit apps.
-/// Data is stored in `~/.config/[appName]/settings.json`.
+/// Data is stored in `$XDG_CONFIG_HOME/[appName]/settings.json`
+/// or `~/.config/[appName]/settings.json` as fallback.
 public final class JSONFileStorage: StorageBackend, @unchecked Sendable {
     /// The shared instance.
     public static let shared = JSONFileStorage()
@@ -45,10 +69,7 @@ public final class JSONFileStorage: StorageBackend, @unchecked Sendable {
 
     /// Creates a JSON file storage with default location.
     public init() {
-        let appName = ProcessInfo.processInfo.processName
-        let configDir = FileManager.default.homeDirectoryForCurrentUser
-            .appendingPathComponent(".config")
-            .appendingPathComponent(appName)
+        let configDir = appConfigDirectory()
 
         // Create directory if needed
         try? FileManager.default.createDirectory(at: configDir, withIntermediateDirectories: true)
@@ -125,7 +146,7 @@ public final class JSONFileStorage: StorageBackend, @unchecked Sendable {
     }
 
     private func saveToDiskAsync() {
-        DispatchQueue.global(qos: .utility).async { [weak self] in
+        Task.detached(priority: .utility) { [weak self] in
             self?.saveToDiskSync()
         }
     }
@@ -327,10 +348,7 @@ public struct SceneStorage<Value: Codable>: @unchecked Sendable {
 
     /// Scene-specific storage file.
     private static var sceneStorage: JSONFileStorage {
-        let appName = ProcessInfo.processInfo.processName
-        let configDir = FileManager.default.homeDirectoryForCurrentUser
-            .appendingPathComponent(".config")
-            .appendingPathComponent(appName)
+        let configDir = appConfigDirectory()
 
         try? FileManager.default.createDirectory(at: configDir, withIntermediateDirectories: true)
 

Sources/TUIKit/Rendering/Terminal.swift

@@ -7,12 +7,24 @@
 
 import Foundation
 
-#if os(Linux)
+#if canImport(Glibc)
     import Glibc
-#else
+#elseif canImport(Musl)
+    import Musl
+#elseif canImport(Darwin)
     import Darwin
 #endif
 
+/// Platform-specific type for `termios` flag fields.
+///
+/// Darwin uses `UInt` (64-bit), Linux uses `tcflag_t` (`UInt32`).
+/// This typealias ensures flag bitmask operations compile on both.
+#if os(Linux)
+    private typealias TermFlag = UInt32
+#else
+    private typealias TermFlag = UInt
+#endif
+
 /// Represents the terminal and controls input and output.
 ///
 /// `Terminal` is the central interface to the terminal. It provides:
@@ -57,7 +69,7 @@ public final class Terminal: @unchecked Sendable {
     public func getSize() -> (width: Int, height: Int) {
         var windowSize = winsize()
 
-        #if os(Linux)
+        #if canImport(Glibc) || canImport(Musl)
             let result = ioctl(STDOUT_FILENO, UInt(TIOCGWINSZ), &windowSize)
         #else
             let result = ioctl(STDOUT_FILENO, TIOCGWINSZ, &windowSize)
@@ -94,7 +106,7 @@ public final class Terminal: @unchecked Sendable {
         // ICANON: Canonical mode (line by line)
         // ISIG: Ctrl+C/Ctrl+Z signals
         // IEXTEN: Ctrl+V
-        raw.c_lflag &= ~(UInt(ECHO | ICANON | ISIG | IEXTEN))
+        raw.c_lflag &= ~TermFlag(ECHO | ICANON | ISIG | IEXTEN)
 
         // Disable:
         // IXON: Ctrl+S/Ctrl+Q software flow control
@@ -102,13 +114,13 @@ public final class Terminal: @unchecked Sendable {
         // BRKINT: Break signal
         // INPCK: Parity check
         // ISTRIP: Strip 8th bit
-        raw.c_iflag &= ~(UInt(IXON | ICRNL | BRKINT | INPCK | ISTRIP))
+        raw.c_iflag &= ~TermFlag(IXON | ICRNL | BRKINT | INPCK | ISTRIP)
 
         // Disable output processing
-        raw.c_oflag &= ~(UInt(OPOST))
+        raw.c_oflag &= ~TermFlag(OPOST)
 
         // Set character size to 8 bits
-        raw.c_cflag |= UInt(CS8)
+        raw.c_cflag |= TermFlag(CS8)
 
         // Set timeouts: VMIN=0, VTIME=1 (100ms timeout)
         // c_cc is a tuple in Swift, so we need to use withUnsafeMutablePointer