feat: add OpenCode/Codex outputs and update changelog (#104)

* Add OpenCode converter coverage and specs

* Add Codex target support and spec docs

* Generate Codex command skills and refresh spec docs

* Add global Codex install path

* fix: harden plugin path loading and codex descriptions

* feat: ensure codex agents block on convert/install

* docs: clarify target branch usage for review

* chore: prep npm package metadata and release notes

* docs: mention opencode and codex in changelog

* docs: update CLI usage and remove stale todos

* feat: install from GitHub with global outputs

src/utils/frontmatter.ts

@@ -0,0 +1,65 @@
+import { load } from "js-yaml"
+
+export type FrontmatterResult = {
+  data: Record<string, unknown>
+  body: string
+}
+
+export function parseFrontmatter(raw: string): FrontmatterResult {
+  const lines = raw.split(/\r?\n/)
+  if (lines.length === 0 || lines[0].trim() !== "---") {
+    return { data: {}, body: raw }
+  }
+
+  let endIndex = -1
+  for (let i = 1; i < lines.length; i += 1) {
+    if (lines[i].trim() === "---") {
+      endIndex = i
+      break
+    }
+  }
+
+  if (endIndex === -1) {
+    return { data: {}, body: raw }
+  }
+
+  const yamlText = lines.slice(1, endIndex).join("\n")
+  const body = lines.slice(endIndex + 1).join("\n")
+  const parsed = load(yamlText)
+  const data = (parsed && typeof parsed === "object") ? (parsed as Record<string, unknown>) : {}
+  return { data, body }
+}
+
+export function formatFrontmatter(data: Record<string, unknown>, body: string): string {
+  const yaml = Object.entries(data)
+    .filter(([, value]) => value !== undefined)
+    .map(([key, value]) => formatYamlLine(key, value))
+    .join("\n")
+
+  if (yaml.trim().length === 0) {
+    return body
+  }
+
+  return [`---`, yaml, `---`, "", body].join("\n")
+}
+
+function formatYamlLine(key: string, value: unknown): string {
+  if (Array.isArray(value)) {
+    const items = value.map((item) => `  - ${formatYamlValue(item)}`)
+    return [key + ":", ...items].join("\n")
+  }
+  return `${key}: ${formatYamlValue(value)}`
+}
+
+function formatYamlValue(value: unknown): string {
+  if (value === null || value === undefined) return ""
+  if (typeof value === "number" || typeof value === "boolean") return String(value)
+  const raw = String(value)
+  if (raw.includes("\n")) {
+    return `|\n${raw.split("\n").map((line) => `  ${line}`).join("\n")}`
+  }
+  if (raw.includes(":") || raw.startsWith("[") || raw.startsWith("{")) {
+    return JSON.stringify(raw)
+  }
+  return raw
+}