refactor(opencode-skill-loader): split loader and merger into focused modules

Extract skill loading pipeline into single-responsibility modules:
- skill-discovery.ts, skill-directory-loader.ts, skill-deduplication.ts
- loaded-skill-from-path.ts, loaded-skill-template-extractor.ts
- skill-template-resolver.ts, skill-definition-record.ts
- git-master-template-injection.ts, allowed-tools-parser.ts
- skill-mcp-config.ts, skill-resolution-options.ts
- merger/ directory for skill merging logic

src/features/opencode-skill-loader/loaded-skill-template-extractor.ts

@@ -0,0 +1,12 @@
+import { readFileSync } from "node:fs"
+import { parseFrontmatter } from "../../shared/frontmatter"
+import type { LoadedSkill } from "./types"
+
+export function extractSkillTemplate(skill: LoadedSkill): string {
+	if (skill.path) {
+		const content = readFileSync(skill.path, "utf-8")
+		const { body } = parseFrontmatter(content)
+		return body.trim()
+	}
+	return skill.definition.template || ""
+}