use GITHUB_REPOSITORY for context

utils/repo-context.ts

@@ -0,0 +1,22 @@
+export interface RepoContext {
+  owner: string;
+  name: string;
+}
+
+/**
+ * Resolve repository context from GITHUB_REPOSITORY environment variable.
+ * Throws if not available.
+ */
+export function resolveRepoContext(): RepoContext {
+  const githubRepo = process.env.GITHUB_REPOSITORY;
+  if (!githubRepo) {
+    throw new Error('GITHUB_REPOSITORY environment variable is required');
+  }
+  
+  const [owner, name] = githubRepo.split('/');
+  if (!owner || !name) {
+    throw new Error(`Invalid GITHUB_REPOSITORY format: ${githubRepo}. Expected 'owner/repo'`);
+  }
+  
+  return { owner, name };
+}