Add MyCodex: a cross-platform desktop app for the @openai/codex engine

mycodex/.gitignore

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+node_modules/
+dist/
+release/
+out/
+*.log
+.DS_Store

mycodex/README.md

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+# MyCodex
+
+A cross-platform **desktop app for the open-source [`@openai/codex`](https://www.npmjs.com/package/@openai/codex) engine**, built with Electron.
+
+MyCodex gives the official Codex CLI a real desktop home: a sessions sidebar, a
+working-folder picker, an interrupt control, and the full Codex agent running in
+an embedded terminal — so sending a message, approving a file edit, viewing a
+diff, interrupting a turn, and restoring a session after a restart all happen in
+one window.
+
+> Built and tested on Linux (x86_64). Build configs for macOS and Windows are
+> included; see [Cross-platform notes](#cross-platform-notes).
+
+## Why an embedded terminal?
+
+The Codex engine is a self-contained Rust binary that ships a rich terminal UI
+(approvals, inline diffs, streaming output, `Esc` to interrupt, `codex resume`
+to restore). Rather than re-implement and inevitably drift from that interaction
+logic, MyCodex drives the **real** engine inside an embedded terminal
+([xterm.js](https://xtermjs.org/) + [node-pty](https://github.com/microsoft/node-pty)).
+You get the authentic Codex behaviour, wrapped in a native desktop shell.
+
+## The three packaging pitfalls (and how MyCodex handles them)
+
+These bite every Electron app that spawns a bundled CLI. MyCodex addresses all
+three:
+
+1. **GUI launches get a crippled `PATH` and no `TERM`.** Apps launched from
+   Finder / a desktop launcher don't inherit your login shell's environment, so
+   the engine (and the shell commands it runs) break. `src/main/env.js`
+   reconstructs a real environment by asking your login shell to print its `env`
+   (`$SHELL -ilc 'env'`), then layers in sane defaults (`TERM=xterm-256color`,
+   common `bin` dirs, UTF-8 locale) before spawning the engine.
+2. **`asar:false` so the bundled binary is spawnable.** A binary packed inside
+   an `app.asar` archive cannot be `exec`'d. The electron-builder config sets
+   `"asar": false` so the engine and node-pty's helper stay as real files on
+   disk.
+3. **node-pty's `spawn-helper` needs `+x`.** Packaging frequently drops the
+   executable bit on node-pty's POSIX `spawn-helper` and on the engine binary.
+   `scripts/fix-pty-permissions.js` re-asserts it at install time, and
+   `src/main/main.js` does it again at startup.
+
+## Project layout
+
+```
+mycodex/
+  src/
+    main/
+      main.js     Electron main process: window, IPC, PTY lifecycle
+      env.js      Login-shell PATH/TERM reconstruction (pitfall #1)
+      codex.js    Locate the bundled engine binary + read session files
+    preload/
+      preload.js  contextBridge API (no nodeIntegration in the renderer)
+    renderer/
+      index.html  App shell (sidebar + terminal pane)
+      renderer.js xterm wiring, sessions list, controls
+      styles.css  Codex-style dark theme
+  scripts/
+    build-renderer.js        Bundle the renderer with esbuild
+    fix-pty-permissions.js   chmod +x spawn-helper / engine (pitfall #3)
+  assets/icon.png
+  package.json
+```
+
+## Develop / run
+
+```bash
+npm install            # installs Electron, node-pty, xterm, and the engine
+npm run rebuild        # rebuild node-pty against Electron's ABI
+npm start              # bundle the renderer and launch the app
+```
+
+On first launch the embedded terminal shows the engine's sign-in screen
+(ChatGPT, device code, or API key) exactly as the CLI does. Authentication is
+handled entirely by the engine — MyCodex never stores or hardcodes credentials.
+If you've already run `codex login`, your existing `~/.codex/auth.json` is reused
+automatically.
+
+## Build / package
+
+```bash
+npm run dist:linux     # AppImage + unpacked dir under release/
+```
+
+## Cross-platform notes
+
+`electron-builder` targets are configured for Linux (AppImage), macOS, and
+Windows. The engine binary is resolved per-platform from
+`@openai/codex-<platform>-<arch>` at runtime (`src/main/codex.js`), mirroring the
+official launcher. macOS/Windows artifacts must be produced on (or cross-built
+for) their respective platforms.
+
+## License
+
+MIT