Allow subtree cancel without reason

Co-Authored-By: Paperclip <noreply@paperclip.ing>

ui/src/pages/IssueDetail.test.tsx

@@ -1150,11 +1150,24 @@ describe("IssueDetail", () => {
       .find((element) =>
         typeof element.className === "string"
         && element.className.includes("overflow-y-auto")
-        && element.textContent?.includes("Reason (required)"),
+        && element.textContent?.includes("Reason (optional)"),
       );
     expect(bodyScrollRegion?.className).toContain("min-h-0");
     expect(bodyScrollRegion?.className).toContain("overscroll-contain");
 
+    const cancelApplyButton = Array.from(dialogContent!.querySelectorAll("button"))
+      .find((button) => button.textContent?.trim() === "Cancel 24 issues") as HTMLButtonElement | undefined;
+    expect(cancelApplyButton).toBeTruthy();
+    expect(cancelApplyButton!.disabled).toBe(true);
+
+    const confirmationCheckbox = dialogContent!.querySelector('input[type="checkbox"]') as HTMLInputElement | null;
+    expect(confirmationCheckbox).toBeTruthy();
+    await act(async () => {
+      confirmationCheckbox!.click();
+    });
+    await flushReact();
+    expect(cancelApplyButton!.disabled).toBe(false);
+
     const footer = Array.from(dialogContent!.querySelectorAll("div"))
       .find((element) =>
         typeof element.className === "string"

ui/src/pages/IssueDetail.tsx

@@ -2702,7 +2702,7 @@ export function IssueDetail() {
   const canApplyTreeControl =
     Boolean(treeControlPreview)
     && !treeControlPreviewLoading
-    && (treeControlMode !== "cancel" || (treeControlReason.trim().length > 0 && treeControlCancelConfirmed));
+    && (treeControlMode !== "cancel" || treeControlCancelConfirmed);
   const attachmentUploadButton = (
     <>
       <input
@@ -3447,7 +3447,7 @@ export function IssueDetail() {
 
             <div className="space-y-1.5">
               <label className="text-xs text-muted-foreground">
-                {treeControlMode === "cancel" ? "Reason (required)" : "Reason (optional)"}
+                Reason (optional)
               </label>
               <Textarea
                 value={treeControlReason}