feat(postinstall): dump full .mcp.json snippet after global npm install

Runs after `npm install -g codesys-mcp-sp21-plus`. Detects every
CODESYS install on PATH and prints the ready-to-paste .mcp.json
block per install (same output as `--print-config`).

Guards:
- Skipped during local installs / dev clones (npm_config_global != true)
- Skipped in CI (CI=true or npm_config_ci=true)
- Wrapped in try/catch + 'node ... || true' so a banner failure never
  blocks the install
- Non-Windows: prints a note and exits cleanly
- Zero CODESYS installs: prints a hint pointing at --print-config

Resolves the awkward 'now run these two commands to verify and get
your config' step from the README.

package.json

@@ -16,7 +16,8 @@
     "test": "vitest --run",
     "test:watch": "vitest",
     "typecheck": "tsc --noEmit",
-    "prepublishOnly": "npm run build && npm test"
+    "prepublishOnly": "npm run build && npm test",
+    "postinstall": "node dist/postinstall.js || true"
   },
   "keywords": [
     "codesys",

src/postinstall.ts

@@ -0,0 +1,88 @@
+#!/usr/bin/env node
+/**
+ * Runs after `npm install [-g] codesys-mcp-sp21-plus`.
+ *
+ * Goals:
+ *   - Confirm to the user that the install worked + show the version
+ *   - Dump the FULL ready-to-paste .mcp.json snippet for every detected install
+ *   - Stay silent during dev (`npm install` inside a clone of the repo) and
+ *     during CI to avoid polluting output.
+ *
+ * Failure-tolerant: any error (no Windows, no CODESYS, fs perms) is caught
+ * and downgraded to a friendly note. We never block the install.
+ */
+
+function isDevOrCi(): boolean {
+  // Skip during local installs / dev clones.
+  if (process.env.npm_config_global !== 'true') return true;
+  // Skip in CI.
+  if (process.env.CI === 'true') return true;
+  if (process.env.npm_config_ci === 'true') return true;
+  return false;
+}
+
+async function main(): Promise<void> {
+  if (isDevOrCi()) {
+    return;
+  }
+
+  let version = 'unknown';
+  try {
+    // eslint-disable-next-line @typescript-eslint/no-var-requires
+    version = require('../package.json').version;
+  } catch {
+    // ignore
+  }
+
+  process.stdout.write(`\n=== codesys-mcp-sp21-plus v${version} installed ===\n\n`);
+
+  if (process.platform !== 'win32') {
+    process.stdout.write(
+      `(CODESYS detection only runs on Windows -- this server requires Windows + CODESYS.)\n\n`
+    );
+    return;
+  }
+
+  let installs: Array<{ serverName: string; profileName: string }>;
+  let printConfig: (
+    installs: unknown[],
+    opts?: Record<string, unknown>
+  ) => string;
+  try {
+    // eslint-disable-next-line @typescript-eslint/no-var-requires
+    const detectMod = require('./detect');
+    installs = detectMod.detectInstalls();
+    printConfig = detectMod.printConfig;
+  } catch (err) {
+    process.stdout.write(
+      `(CODESYS install detection failed: ${(err as Error).message})\n\n`
+    );
+    return;
+  }
+
+  if (installs.length === 0) {
+    process.stdout.write(
+      `No CODESYS installations detected under "C:\\Program Files" / "C:\\Program Files (x86)".\n` +
+      `Install CODESYS first, then run \`codesys-mcp-sp21-plus --print-config\` to generate\n` +
+      `the .mcp.json snippet.\n\n`
+    );
+    return;
+  }
+
+  process.stdout.write(`Add the following to your .mcp.json (Claude Code configuration):\n\n`);
+  try {
+    process.stdout.write(printConfig(installs) + '\n\n');
+  } catch (err) {
+    process.stdout.write(`(printConfig failed: ${(err as Error).message})\n\n`);
+    return;
+  }
+  process.stdout.write(
+    `Re-run anytime with: codesys-mcp-sp21-plus --print-config\n` +
+    `Filter to one SP family with:  codesys-mcp-sp21-plus --print-config --sp 22\n\n`
+  );
+}
+
+main().catch((err) => {
+  // Never fail the install over a banner.
+  process.stdout.write(`\n(post-install banner failed: ${(err as Error).message})\n\n`);
+});