fix: allow direct_prompt with issue assignment without requiring assignee_trigger (#192)

- Modified validation logic to only require assignee_trigger when direct_prompt is not provided
- Made assigneeTrigger optional in IssueAssignedEvent type definition
- Enhanced context generation to handle missing assigneeTrigger gracefully
- Added comprehensive test coverage for the new behavior

This enables direct_prompt workflows on issue assignment events without
requiring assignee_trigger configuration, fixing the error:
"ASSIGNEE_TRIGGER is required for issue assigned event"

Fixes #113

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-authored-by: Claude <noreply@anthropic.com>

src/create-prompt/index.ts

@@ -242,7 +242,7 @@ export function prepareContext(
       }
 
       if (eventAction === "assigned") {
-        if (!assigneeTrigger) {
+        if (!assigneeTrigger && !directPrompt) {
           throw new Error(
             "ASSIGNEE_TRIGGER is required for issue assigned event",
           );
@@ -254,7 +254,7 @@ export function prepareContext(
           issueNumber,
           baseBranch,
           claudeBranch,
-          assigneeTrigger,
+          ...(assigneeTrigger && { assigneeTrigger }),
         };
       } else if (eventAction === "opened") {
         eventData = {
@@ -331,7 +331,9 @@ export function getEventTypeAndContext(envVars: PreparedContext): {
       }
       return {
         eventType: "ISSUE_ASSIGNED",
-        triggerContext: `issue assigned to '${eventData.assigneeTrigger}'`,
+        triggerContext: eventData.assigneeTrigger
+          ? `issue assigned to '${eventData.assigneeTrigger}'`
+          : `issue assigned event`,
       };
 
     case "pull_request":

src/create-prompt/types.ts

@@ -65,7 +65,7 @@ type IssueAssignedEvent = {
   issueNumber: string;
   baseBranch: string;
   claudeBranch: string;
-  assigneeTrigger: string;
+  assigneeTrigger?: string;
 };
 
 type PullRequestEvent = {