feat: make each plugin an npm workspace built by a termix-plugin CLI

packages/plugin-sdk/cli/lib/plugin-dir.mjs

@@ -0,0 +1,29 @@
+import fs from "node:fs";
+import path from "node:path";
+
+export function readManifest(cwd) {
+  const manifestPath = path.join(cwd, "manifest.json");
+  if (!fs.existsSync(manifestPath)) {
+    throw new Error(`No manifest.json in ${cwd}`);
+  }
+  try {
+    return JSON.parse(fs.readFileSync(manifestPath, "utf8"));
+  } catch (error) {
+    throw new Error(`manifest.json is not valid JSON: ${error.message}`);
+  }
+}
+
+/** The first of these that exists, or null. */
+export function resolveEntry(cwd, candidates) {
+  for (const candidate of candidates) {
+    const full = path.join(cwd, candidate);
+    if (fs.existsSync(full)) return full;
+  }
+  return null;
+}
+
+export function copyDir(from, to) {
+  if (!fs.existsSync(from)) return false;
+  fs.cpSync(from, to, { recursive: true });
+  return true;
+}