Add standalone executable packaging with esbuild + pkg

- Add npm scripts for building Windows/Linux/macOS executables
- Replace uuid package with crypto.randomUUID() for ESM compatibility
- Use esbuild to pre-bundle code before pkg (fixes MCP SDK subpath exports)
- Update CLI name from 'memory' to 'cortex'
- Update USAGE.md with build instructions and standalone setup
- Add bundle/ and build/ to .gitignore

.gitignore

@@ -1,3 +1,5 @@
 node_modules/
 dist/
+bundle/
+build/
 .memory/