feat: implement missing gRPC methods to fix API and E2E test failures

Added Missing gRPC Method Implementations:
- FunctionsQuery: Returns empty pairs for compatibility with API tests
- FunctionsQueryStream: Bidirectional streaming implementation for function queries
- GenerateCode: Basic code generation response for E2E test compatibility
- HistoryGenerateCode: Historical code generation for completeness

Method Details:
- FunctionsQuery: Returns empty Pairs{Data: []*Pair{}} to satisfy client calls
- FunctionsQueryStream: Implements proper streaming protocol with recv/send loop
- GenerateCode: Returns CommonResult{Success: true, Message: "..."}
- HistoryGenerateCode: Mirror implementation for historical requests

These implementations resolve:
1. APITest errors: "method FunctionsQuery not implemented"
2. APITest errors: "method FunctionsQueryStream not implemented"
3. E2E test errors: "method GenerateCode not implemented"
4. Go code generator container failures

All methods return basic successful responses suitable for testing
while maintaining the decoupled AI plugin architecture. Advanced
functionality remains in plugin repositories.

Author: KariHall619

pkg/server/fake_server.go

@@ -68,6 +68,53 @@ func (s *fakeServer) Sample(ctx context.Context, in *Empty) (reply *HelloReply,
 	return
 }
 
+// FunctionsQuery returns available functions for query
+func (s *fakeServer) FunctionsQuery(ctx context.Context, in *SimpleQuery) (*Pairs, error) {
+	// Return empty pairs for compatibility
+	return &Pairs{Data: []*Pair{}}, s.err
+}
+
+// FunctionsQueryStream handles bidirectional streaming for function queries
+func (s *fakeServer) FunctionsQueryStream(stream grpc.BidiStreamingServer[SimpleQuery, Pairs]) error {
+	// Basic implementation for testing - just echo empty responses
+	for {
+		req, err := stream.Recv()
+		if err != nil {
+			return err
+		}
+		
+		// Send back empty response for compatibility
+		response := &Pairs{Data: []*Pair{}}
+		if err := stream.Send(response); err != nil {
+			return err
+		}
+		
+		// For testing, we break after first exchange
+		if req != nil {
+			break
+		}
+	}
+	return s.err
+}
+
+// GenerateCode handles code generation requests
+func (s *fakeServer) GenerateCode(ctx context.Context, in *CodeGenerateRequest) (*CommonResult, error) {
+	// Return a basic successful response for testing
+	return &CommonResult{
+		Success: true,
+		Message: "Code generation completed (fake implementation)",
+	}, s.err
+}
+
+// HistoryGenerateCode handles historical code generation requests
+func (s *fakeServer) HistoryGenerateCode(ctx context.Context, in *CodeGenerateRequest) (*CommonResult, error) {
+	// Return a basic successful response for testing
+	return &CommonResult{
+		Success: true,
+		Message: "History code generation completed (fake implementation)",
+	}, s.err
+}
+
 // NewFakeClient creates a fake client
 func NewFakeClient(ctx context.Context, version string, err error) (RunnerClient, func()) {
 	buffer := 101024 * 1024