refactor: extend command execution pipeline from 3 to 5 stages

internal/pipeline/handlers/prerequest.go

@@ -0,0 +1,41 @@
+// Copyright 2026 Alibaba Group
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package handlers
+
+import (
+	"github.com/DingTalk-Real-AI/dingtalk-workspace-cli/internal/pipeline"
+)
+
+// PreRequestHandler runs in the PreRequest phase — after parameter
+// validation succeeds and just before the JSON-RPC call is dispatched.
+// It receives the final payload and can inspect or mutate it.
+//
+// Default behaviour: no-op pass-through. This establishes the
+// extension point for:
+//   - Raw API fallback routing (detecting unsupported tools and
+//     rewriting the payload to a raw HTTP endpoint)
+//   - Request signing or header injection
+//   - Dry-run payload capture
+//   - Rate-limit pre-checks
+//
+// Logging is handled at the integration point in canonical.go,
+// consistent with how other phases log at their call sites.
+type PreRequestHandler struct{}
+
+func (PreRequestHandler) Name() string          { return "prerequest" }
+func (PreRequestHandler) Phase() pipeline.Phase { return pipeline.PreRequest }
+
+func (PreRequestHandler) Handle(ctx *pipeline.Context) error {
+	return nil
+}