Phase 4: add readSkillBody — SKILL.md read with frontmatter strip.

Mirror agent-session _expandSkillCommand body extraction via public stripFrontmatter API (SPEC §5.3, §10).

Co-authored-by: Cursor <cursoragent@cursor.com>

src/expand.ts

@@ -0,0 +1,8 @@
+import { readFileSync } from "node:fs";
+import { stripFrontmatter } from "@earendil-works/pi-coding-agent";
+
+/** mirror agent-session `_expandSkillCommand` — SKILL.md body without YAML frontmatter (SPEC §5.3, §10). */
+export function readSkillBody(filePath: string): string {
+	const content = readFileSync(filePath, "utf-8");
+	return stripFrontmatter(content).trim();
+}