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/files.ts

@@ -0,0 +1,64 @@
+import { promises as fs } from "fs"
+import path from "path"
+
+export async function pathExists(filePath: string): Promise<boolean> {
+  try {
+    await fs.access(filePath)
+    return true
+  } catch {
+    return false
+  }
+}
+
+export async function ensureDir(dirPath: string): Promise<void> {
+  await fs.mkdir(dirPath, { recursive: true })
+}
+
+export async function readText(filePath: string): Promise<string> {
+  return fs.readFile(filePath, "utf8")
+}
+
+export async function readJson<T>(filePath: string): Promise<T> {
+  const raw = await readText(filePath)
+  return JSON.parse(raw) as T
+}
+
+export async function writeText(filePath: string, content: string): Promise<void> {
+  await ensureDir(path.dirname(filePath))
+  await fs.writeFile(filePath, content, "utf8")
+}
+
+export async function writeJson(filePath: string, data: unknown): Promise<void> {
+  const content = JSON.stringify(data, null, 2)
+  await writeText(filePath, content + "\n")
+}
+
+export async function walkFiles(root: string): Promise<string[]> {
+  const entries = await fs.readdir(root, { withFileTypes: true })
+  const results: string[] = []
+  for (const entry of entries) {
+    const fullPath = path.join(root, entry.name)
+    if (entry.isDirectory()) {
+      const nested = await walkFiles(fullPath)
+      results.push(...nested)
+    } else if (entry.isFile()) {
+      results.push(fullPath)
+    }
+  }
+  return results
+}
+
+export async function copyDir(sourceDir: string, targetDir: string): Promise<void> {
+  await ensureDir(targetDir)
+  const entries = await fs.readdir(sourceDir, { withFileTypes: true })
+  for (const entry of entries) {
+    const sourcePath = path.join(sourceDir, entry.name)
+    const targetPath = path.join(targetDir, entry.name)
+    if (entry.isDirectory()) {
+      await copyDir(sourcePath, targetPath)
+    } else if (entry.isFile()) {
+      await ensureDir(path.dirname(targetPath))
+      await fs.copyFile(sourcePath, targetPath)
+    }
+  }
+}