Clarify issue type form routing

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

Copilot-Session: ea8faa5c-7f26-4e2d-bf9c-6f0b5f173e8c

Author: zwick

pkg/github/issues.go

@@ -2047,14 +2047,6 @@ var issueWriteFormParams = map[string]struct{}{
 	"_ui_submitted": {},
 }
 
-func shouldIssueWriteDeferToForm(ctx context.Context, deps ToolDependencies, req *mcp.CallToolRequest, args map[string]any) bool {
-	issueType, issueTypeProvided, err := OptionalParamOK[string](args, "type")
-	explicitTypeClear := err == nil && issueTypeProvided && issueType == "" && args["method"] == "update"
-	// The form cannot preserve an empty type, so execute the complete call
-	// directly to avoid dropping the clear or any co-submitted values.
-	return !explicitTypeClear && shouldDeferToForm(ctx, deps, req, args, issueWriteFormParams)
-}
-
 // issueWriteAwaitingFormResult builds the "awaiting form submission" stub
 // returned when issue_write hands off to the MCP App form. The body is shared
 // by IssueWrite and LegacyIssueWrite. The result is marked IsError=true so
@@ -2232,7 +2224,15 @@ Options are:
 
 			// Hand off to the interactive MCP App form unless this call must
 			// execute now (see shouldDeferToForm).
-			if shouldIssueWriteDeferToForm(ctx, deps, req, args) {
+			deferToForm := shouldDeferToForm(ctx, deps, req, args, issueWriteFormParams)
+			if method == "update" {
+				if issueType, ok := args["type"].(string); ok && issueType == "" {
+					// The form replaces an empty type with the current type, so execute
+					// directly to preserve the clear and any co-submitted values.
+					deferToForm = false
+				}
+			}
+			if deferToForm {
 				issueNumber := 0
 				if method == "update" {
 					n, numErr := RequiredInt(args, "issue_number")