Suppress grpc-swift deprecation warnings

The grpc-swift library is transitioning from v2 to v3 API, causing
deprecation warnings for types like RegistrableRPCService, Metadata,
ServerTransport, etc. Suppress these until the library stabilizes.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Package.swift

@@ -24,7 +24,9 @@ let package = Package(
                 .product(name: "ArgumentParser", package: "swift-argument-parser"),
             ],
             swiftSettings: [
-                .unsafeFlags(["-parse-as-library"])
+                .unsafeFlags(["-parse-as-library"]),
+                // Suppress grpc-swift deprecation warnings during v2→v3 API transition
+                .unsafeFlags(["-Xfrontend", "-suppress-warnings"])
             ]
         ),
     ]