feat: add skills extraction to --from-af import (#823)

Co-authored-by: Letta <noreply@letta.com>

src/agent/github-utils.ts

@@ -0,0 +1,61 @@
+/**
+ * Shared GitHub API utilities for skills import/export
+ */
+
+export interface GitHubEntry {
+  type: "file" | "dir";
+  name: string;
+  path: string;
+  download_url?: string;
+}
+
+/**
+ * Fetch GitHub contents using gh CLI (authenticated) or direct API
+ * Returns array of directory/file entries
+ */
+export async function fetchGitHubContents(
+  owner: string,
+  repo: string,
+  branch: string,
+  path: string,
+): Promise<GitHubEntry[]> {
+  const apiPath = path
+    ? `repos/${owner}/${repo}/contents/${path}?ref=${branch}`
+    : `repos/${owner}/${repo}/contents?ref=${branch}`;
+
+  // Try gh CLI (authenticated, 5000 req/hr)
+  try {
+    const { execSync } = await import("node:child_process");
+    const result = execSync(`gh api ${apiPath}`, {
+      encoding: "utf-8",
+      stdio: ["pipe", "pipe", "ignore"],
+    });
+    return JSON.parse(result) as GitHubEntry[];
+  } catch {
+    // Fall back to unauthenticated API (60 req/hr)
+  }
+
+  // Try direct API
+  const url = `https://api.github.com/repos/${owner}/${repo}/contents/${path}?ref=${branch}`;
+  const response = await fetch(url, {
+    headers: {
+      Accept: "application/vnd.github.v3+json",
+      "User-Agent": "letta-code",
+    },
+  });
+
+  if (!response.ok) {
+    throw new Error(
+      `Failed to fetch from ${owner}/${repo}/${branch}/${path}: ${response.statusText}`,
+    );
+  }
+
+  return (await response.json()) as GitHubEntry[];
+}
+
+/**
+ * Extract directory names from GitHub entries
+ */
+export function parseDirNames(entries: GitHubEntry[]): Set<string> {
+  return new Set(entries.filter((e) => e.type === "dir").map((e) => e.name));
+}