feat(macOS): add gateway password auth support and fix Swift 6.2 concurrency

- Add CLAWDIS_GATEWAY_PASSWORD to launchd plist environment
- Read password from gateway.remote.password config in client
- Fix Swift 6.2 sending parameter violations in config save functions
- Add password parameter to GatewayConnection.Config type
- GatewayChannel now sends password in connect auth params
- GatewayEndpointStore and GatewayLaunchAgentManager read password from config
- CLI gateway client reads password from remote config and env

apps/macos/Sources/Clawdis/GatewayLaunchAgentManager.swift

@@ -64,6 +64,7 @@ enum GatewayLaunchAgentManager {
             .joined(separator: ":")
         let bind = self.preferredGatewayBind() ?? "loopback"
         let token = self.preferredGatewayToken()
+        let password = self.preferredGatewayPassword()
         var envEntries = """
             <key>PATH</key>
             <string>\(preferredPath)</string>
@@ -76,6 +77,12 @@ enum GatewayLaunchAgentManager {
                 <string>\(token)</string>
             """
         }
+        if let password {
+            envEntries += """
+                <key>CLAWDIS_GATEWAY_PASSWORD</key>
+                <string>\(password)</string>
+            """
+        }
         let plist = """
         <?xml version="1.0" encoding="UTF-8"?>
         <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
@@ -146,6 +153,24 @@ enum GatewayLaunchAgentManager {
         return trimmed.isEmpty ? nil : trimmed
     }
 
+    private static func preferredGatewayPassword() -> String? {
+        // First check environment variable
+        let raw = ProcessInfo.processInfo.environment["CLAWDIS_GATEWAY_PASSWORD"] ?? ""
+        let trimmed = raw.trimmingCharacters(in: .whitespacesAndNewlines)
+        if !trimmed.isEmpty {
+            return trimmed
+        }
+        // Then check config file (gateway.auth.password)
+        let root = ClawdisConfigFile.loadDict()
+        if let gateway = root["gateway"] as? [String: Any],
+           let auth = gateway["auth"] as? [String: Any],
+           let password = auth["password"] as? String
+        {
+            return password.trimmingCharacters(in: .whitespacesAndNewlines)
+        }
+        return nil
+    }
+
     private struct LaunchctlResult {
         let status: Int32
         let output: String