fix(go): remove hand-written PermissionRequest that conflicts with generated type

The @github/copilot 0.0.421 schema update (PR #684) caused quicktype to
generate a PermissionRequest struct in generated_session_events.go that
conflicts with the hand-written one in types.go. The generated type has
all 23+ typed fields while the hand-written one was a simplified wrapper
with an Extra map catch-all.

Remove the hand-written type and its custom UnmarshalJSON in favor of the
generated one. Update the E2E test that accessed Extra["toolName"] to
use the typed ToolName field instead.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: SteveSandersonMS

go/internal/e2e/tools_test.go

@@ -350,8 +350,8 @@ func TestTools(t *testing.T) {
 		for _, req := range permissionRequests {
 			if req.Kind == "custom-tool" {
 				customToolReqs++
-				if toolName, ok := req.Extra["toolName"].(string); !ok || toolName != "encrypt_string" {
-					t.Errorf("Expected toolName 'encrypt_string', got '%v'", req.Extra["toolName"])
+				if req.ToolName == nil || *req.ToolName != "encrypt_string" {
+					t.Errorf("Expected toolName 'encrypt_string', got '%v'", req.ToolName)
 				}
 			}
 		}

go/types.go

@@ -99,39 +99,6 @@ type SystemMessageConfig struct {
 	Content string `json:"content,omitempty"`
 }
 
-// PermissionRequest represents a permission request from the server
-type PermissionRequest struct {
-	Kind       string         `json:"kind"`
-	ToolCallID string         `json:"toolCallId,omitempty"`
-	Extra      map[string]any `json:"-"` // Additional fields vary by kind
-}
-
-// UnmarshalJSON implements custom JSON unmarshaling for PermissionRequest
-// to capture additional fields (varying by kind) into the Extra map.
-func (p *PermissionRequest) UnmarshalJSON(data []byte) error {
-	// Unmarshal known fields via an alias to avoid infinite recursion
-	type Alias PermissionRequest
-	var alias Alias
-	if err := json.Unmarshal(data, &alias); err != nil {
-		return err
-	}
-	*p = PermissionRequest(alias)
-
-	// Unmarshal all fields into a generic map
-	var raw map[string]any
-	if err := json.Unmarshal(data, &raw); err != nil {
-		return err
-	}
-
-	// Remove known fields, keep the rest as Extra
-	delete(raw, "kind")
-	delete(raw, "toolCallId")
-	if len(raw) > 0 {
-		p.Extra = raw
-	}
-	return nil
-}
-
 // PermissionRequestResultKind represents the kind of a permission request result.
 type PermissionRequestResultKind string