fix: require Node 20+ (string-width uses /v regex flag)

README.md

@@ -10,7 +10,7 @@
   <a href="https://www.npmjs.com/package/codeburn"><img src="https://img.shields.io/npm/v/codeburn.svg" alt="npm version" /></a>
   <a href="https://www.npmjs.com/package/codeburn"><img src="https://img.shields.io/npm/dm/codeburn.svg" alt="npm downloads" /></a>
   <a href="https://github.com/agentseal/codeburn/blob/main/LICENSE"><img src="https://img.shields.io/npm/l/codeburn.svg" alt="license" /></a>
-  <a href="https://github.com/agentseal/codeburn"><img src="https://img.shields.io/badge/node-%3E%3D18-brightgreen.svg" alt="node version" /></a>
+  <a href="https://github.com/agentseal/codeburn"><img src="https://img.shields.io/badge/node-%3E%3D20-brightgreen.svg" alt="node version" /></a>
 </p>
 
 <p align="center">
@@ -35,7 +35,7 @@ npx codeburn
 
 ### Requirements
 
-- Node.js 18+
+- Node.js 20+
 - Claude Code (reads `~/.claude/projects/` session data)
 
 ## Usage

package.json

@@ -26,6 +26,9 @@
     "observability",
     "developer-tools"
   ],
+  "engines": {
+    "node": ">=20"
+  },
   "author": "AgentSeal <hello@agentseal.org>",
   "license": "MIT",
   "dependencies": {

tsup.config.ts

@@ -3,7 +3,7 @@ import { defineConfig } from 'tsup'
 export default defineConfig({
   entry: ['src/cli.ts'],
   format: ['esm'],
-  target: 'node18',
+  target: 'node20',
   outDir: 'dist',
   clean: true,
   splitting: false,