fix: add strict YAML validation for plugin frontmatter (#399)

tests/frontmatter.test.ts

@@ -1,4 +1,7 @@
+import { readdirSync, readFileSync, statSync } from "fs"
+import path from "path"
 import { describe, expect, test } from "bun:test"
+import { load } from "js-yaml"
 import { formatFrontmatter, parseFrontmatter } from "../src/utils/frontmatter"
 
 describe("frontmatter", () => {
@@ -17,4 +20,58 @@ describe("frontmatter", () => {
     expect(parsed.data.description).toBe("Test")
     expect(parsed.body.trim()).toBe(body)
   })
+
+})
+
+/**
+ * Collect all markdown files with YAML frontmatter from a plugin directory.
+ * Returns [relativePath, yamlText] pairs for each file with a frontmatter block.
+ */
+function collectFrontmatterFiles(pluginRoot: string): [string, string][] {
+  const results: [string, string][] = []
+
+  function walk(dir: string) {
+    for (const entry of readdirSync(dir, { withFileTypes: true })) {
+      const full = path.join(dir, entry.name)
+      if (entry.isDirectory()) {
+        if (entry.name === "node_modules" || entry.name === ".git") continue
+        walk(full)
+        continue
+      }
+      if (!entry.name.endsWith(".md")) continue
+      const raw = readFileSync(full, "utf8")
+      const lines = raw.split(/\r?\n/)
+      if (lines[0]?.trim() !== "---") continue
+      let end = -1
+      for (let i = 1; i < lines.length; i++) {
+        if (lines[i].trim() === "---") { end = i; break }
+      }
+      if (end === -1) continue
+      const yaml = lines.slice(1, end).join("\n")
+      const rel = path.relative(pluginRoot, full)
+      results.push([rel, yaml])
+    }
+  }
+
+  walk(pluginRoot)
+  return results
+}
+
+describe("frontmatter YAML validity", () => {
+  const pluginRoots = [
+    "plugins/compound-engineering",
+    "plugins/coding-tutor",
+  ]
+
+  for (const pluginRoot of pluginRoots) {
+    const root = path.join(process.cwd(), pluginRoot)
+    try { statSync(root) } catch { continue }
+    const files = collectFrontmatterFiles(root)
+
+    for (const [rel, yaml] of files) {
+      test(`${pluginRoot}/${rel} has valid strict YAML frontmatter`, () => {
+        expect(() => load(yaml)).not.toThrow()
+      })
+    }
+  }
 })