Fix Linear issues showing as unread for the creator

Linear webhook payloads don't include creator/assignee data, so the
author was never resolved and defaulted to the twist ID. This meant
markThreadReadForAuthor always skipped, leaving issues unread for
the user who created them. Now fetches the full issue from the API
in the webhook handler to get the real creator.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: KrisBraun

connectors/linear/src/linear.ts

@@ -721,9 +721,30 @@ export class Linear extends Connector<Linear> {
       return;
     }
 
-    // Use issue data directly from webhook payload
-    const creator = issue.creator || null;
-    const assignee = issue.assignee || null;
+    // Webhook payloads don't include creator/assignee — fetch from API
+    let creator: { id: string; email?: string; name: string; avatarUrl?: string | null } | null = issue.creator || null;
+    let assignee: { id: string; email?: string; name: string; avatarUrl?: string | null } | null = issue.assignee || null;
+
+    if (!creator || !assignee) {
+      try {
+        const client = await this.getClient(projectId);
+        const fullIssue = await client.issue(issueId);
+        if (!creator) {
+          const apiCreator = await fullIssue.creator;
+          if (apiCreator) {
+            creator = { id: apiCreator.id, email: apiCreator.email, name: apiCreator.name, avatarUrl: apiCreator.avatarUrl };
+          }
+        }
+        if (!assignee) {
+          const apiAssignee = await fullIssue.assignee;
+          if (apiAssignee) {
+            assignee = { id: apiAssignee.id, email: apiAssignee.email, name: apiAssignee.name, avatarUrl: apiAssignee.avatarUrl };
+          }
+        }
+      } catch (error) {
+        console.error("Failed to fetch issue from API for creator/assignee:", error);
+      }
+    }
 
     // Build thread update with only issue fields (no notes)
     const authorContact = this.resolveAuthorContact(creator);