feat(mcp): audit recorder wrapper injecting via_mcp + mcp_token_id from ctx

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/mcp/audit_ctx.go

@@ -0,0 +1,45 @@
+package mcp
+
+import (
+	"context"
+
+	"github.com/yan1h/agent-coding-workflow/internal/audit"
+)
+
+type mcpTokenIDCtxKey struct{}
+
+func withMcpTokenID(ctx context.Context, tokenID string) context.Context {
+	return context.WithValue(ctx, mcpTokenIDCtxKey{}, tokenID)
+}
+
+func mcpTokenIDFromCtx(ctx context.Context) string {
+	if v, ok := ctx.Value(mcpTokenIDCtxKey{}).(string); ok {
+		return v
+	}
+	return ""
+}
+
+type wrappedRecorder struct {
+	inner audit.Recorder
+}
+
+// AuditWrap wraps an audit.Recorder so that every Record call automatically
+// injects "via_mcp" and "mcp_token_id" into the entry's Metadata when the
+// context carries an MCP token ID. Returns nil when inner is nil.
+func AuditWrap(inner audit.Recorder) audit.Recorder {
+	if inner == nil {
+		return nil
+	}
+	return &wrappedRecorder{inner: inner}
+}
+
+func (r *wrappedRecorder) Record(ctx context.Context, e audit.Entry) error {
+	if tid := mcpTokenIDFromCtx(ctx); tid != "" {
+		if e.Metadata == nil {
+			e.Metadata = map[string]any{}
+		}
+		e.Metadata["via_mcp"] = true
+		e.Metadata["mcp_token_id"] = tid
+	}
+	return r.inner.Record(ctx, e)
+}