fix: match label_trigger case-insensitively (#1576)

label_trigger used a case-sensitive exact comparison, so a workflow
configured with label_trigger: "claude-task" did not fire when an issue
received a label named "Claude-Task" (the same label name with different
casing).

GitHub label names are unique without regard to case, so comparing without
case is unambiguous. It also matches the trigger_phrase check in the same
function, which is already case-insensitive.

Compare labelName and labelTrigger with toLowerCase(), and add a test
covering a mixed-case label.

Fixes #1571

src/github/validation/trigger.ts

@@ -38,7 +38,10 @@ export function checkContainsTrigger(context: ParsedGitHubContext): boolean {
   if (isIssuesEvent(context) && context.eventAction === "labeled") {
     const labelName = (context.payload as any).label?.name || "";
 
-    if (labelTrigger && labelName === labelTrigger) {
+    if (
+      labelTrigger &&
+      labelName.toLowerCase() === labelTrigger.toLowerCase()
+    ) {
       console.log(`Issue labeled with trigger label '${labelTrigger}'`);
       return true;
     }