add Windows support (Phase 1)

Cross-platform paths: config_dir() uses %APPDATA%, data_dir() uses
%PROGRAMDATA% on Windows. TLS cert directory uses data_dir() instead
of hardcoded /usr/local/var/numa. Windows DNS discovery via ipconfig.
Fixed cfg gates from not(macos) to explicit linux to prevent Linux
code compiling on Windows. Added Windows target to CI and release
workflows with zip packaging.

System integration (numa install/service) not yet supported on Windows
— users run numa.exe manually.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/lib.rs

@@ -21,9 +21,25 @@ pub mod tls;
 pub type Error = Box<dyn std::error::Error + Send + Sync>;
 pub type Result<T> = std::result::Result<T, Error>;
 
-/// Shared config directory: ~/.config/numa/
-/// Handles sudo (uses SUDO_USER) and launchd (falls back to /usr/local/var/numa/).
+/// Shared config directory for persistent data (services.json, etc).
+/// Unix: ~/.config/numa/ (or /usr/local/var/numa/ when running as root daemon)
+/// Windows: %APPDATA%\numa
 pub fn config_dir() -> std::path::PathBuf {
+    #[cfg(windows)]
+    {
+        std::path::PathBuf::from(
+            std::env::var("APPDATA").unwrap_or_else(|_| "C:\\ProgramData".into()),
+        )
+        .join("numa")
+    }
+    #[cfg(not(windows))]
+    {
+        config_dir_unix()
+    }
+}
+
+#[cfg(not(windows))]
+fn config_dir_unix() -> std::path::PathBuf {
     // When run via sudo, SUDO_USER has the real user
     if let Ok(user) = std::env::var("SUDO_USER") {
         let home = if cfg!(target_os = "macos") {
@@ -37,7 +53,6 @@ pub fn config_dir() -> std::path::PathBuf {
     // Normal user (not root)
     if let Ok(home) = std::env::var("HOME") {
         let path = std::path::PathBuf::from(&home);
-        // /var/root on macOS is read-only (SIP), use /usr/local/var/numa instead
         if !home.starts_with("/var/root") && !home.starts_with("/root") {
             return path.join(".config").join("numa");
         }
@@ -46,3 +61,20 @@ pub fn config_dir() -> std::path::PathBuf {
     // Running as root daemon (launchd/systemd) — use system-wide path
     std::path::PathBuf::from("/usr/local/var/numa")
 }
+
+/// System-wide data directory for TLS certs.
+/// Unix: /usr/local/var/numa
+/// Windows: %PROGRAMDATA%\numa
+pub fn data_dir() -> std::path::PathBuf {
+    #[cfg(windows)]
+    {
+        std::path::PathBuf::from(
+            std::env::var("PROGRAMDATA").unwrap_or_else(|_| "C:\\ProgramData".into()),
+        )
+        .join("numa")
+    }
+    #[cfg(not(windows))]
+    {
+        std::path::PathBuf::from("/usr/local/var/numa")
+    }
+}