🐛 Relocate MCP run directory out of the npm-managed install directory

For the npm MCP package, adjust the launcher to specifically prepare
the runtime directory: The package contents are copied once per version
to a runtime directory owned by the launcher.

The npm-owned package directory cannot be used. While installing there
worked for older npm/npx version, we have to assume it is read-only.

Fixes #9947

mcp/bin/mcp-local.js

@@ -1,21 +1,61 @@
 #!/usr/bin/env node
 
+// Entry point (bin) of the published @penpot/mcp package.
+// This script is not intended to be run from a source checkout; there, use
+// `pnpm run bootstrap` directly, as described in the README.
+
 const { execSync } = require("child_process");
 const fs = require("fs");
+const os = require("os");
 const path = require("path");
 
-const root = path.resolve(__dirname, "..");
+const packageRoot = path.resolve(__dirname, "..");
-const pkg = require(path.join(root, "package.json"));
+const pkg = require(path.join(packageRoot, "package.json"));
 
 function pnpmVersion() {
   const match = (pkg.packageManager || "").match(/^pnpm@([^+]+)/);
   return match ? match[1] : "latest";
 }
 
-function run(command) {
+/**
-  execSync(command, { cwd: root, stdio: "inherit" });
+ * Prepares the directory in which to bootstrap and run.
+ *
+ * The package contents are copied once per version to a runtime directory
+ * owned by this launcher. The npm-owned package directory cannot be used;
+ * we have to assume it is read-only (#9947).
+ *
+ * @returns {string} the directory to run the bootstrap in
+ */
+function prepareRuntimeRoot() {
+  const cacheBase = process.env.XDG_CACHE_HOME || path.join(os.homedir(), ".cache");
+  const runtimeRoot = path.join(cacheBase, "penpot-mcp", pkg.version);
+  if (fs.existsSync(runtimeRoot)) {
+    return runtimeRoot;
+  }
+
+  // copy to a temporary sibling first and rename, so an interrupted copy
+  // cannot leave a partial runtime directory behind
+  console.log(`Preparing runtime directory ${runtimeRoot} ...`);
+  const tempRoot = `${runtimeRoot}.tmp-${process.pid}`;
+  fs.rmSync(tempRoot, { recursive: true, force: true });
+  fs.cpSync(packageRoot, tempRoot, {
+    recursive: true,
+    filter: (src) => path.basename(src) !== "node_modules",
+  });
+  try {
+    fs.renameSync(tempRoot, runtimeRoot);
+  } catch (error) {
+    fs.rmSync(tempRoot, { recursive: true, force: true });
+    if (!fs.existsSync(runtimeRoot)) {
+      throw error;
+    }
+    // a concurrent launch created the runtime directory in the meantime; use it
+  }
+  return runtimeRoot;
 }
 
+const root = prepareRuntimeRoot();
+
 // pnpm-lock.yaml is hard-excluded by npm pack; it is shipped as pnpm-lock.dist.yaml
 // and restored here before bootstrap runs.
 const distLock = path.join(root, "pnpm-lock.dist.yaml");
@@ -25,7 +65,7 @@ if (fs.existsSync(distLock)) {
 }
 
 try {
-  run(`npx -y pnpm@${pnpmVersion()} run bootstrap`);
+  execSync(`npx -y pnpm@${pnpmVersion()} run bootstrap`, { cwd: root, stdio: "inherit" });
 } catch (error) {
   process.exit(error.status ?? 1);
 }