fix: ship the native addon inside the macOS .app

[Ernxst]

Harness: Claude Code
Agent: none
Model: anthropic/claude-opus-5

Task statements

1. Compare this fork with a public benchmark of one Mac app built in 21 frameworks, and bring startup closer to plain GPUI. (Working-directory and workflow instructions omitted.)

2. Settle where shipped apps keep the native addon so macOS stops rescanning it. (Working-directory and workflow instructions omitted.)

Closes #601.

The chat example's .app now ships the native addon in Contents/Frameworks instead of embedding it in the executable. An embedded addon is written to $TMPDIR/.bun-*.node and scanned by macOS on the first launch and again after every $TMPDIR purge (342 ms scan, 620–665 ms launches in #601). The bare bun build --compile --production binary still embeds it.

GPUIX Chat.app/Contents
├── MacOS/chat                                   bun build --compile --external '*.node'
├── Frameworks/gpuix-native.darwin-arm64.node    ad-hoc signed
├── Resources/AppIcon.icns
└── Info.plist

The executable is compiled from a generated entry that points napi-rs's loader at the bundled file, then loads the app. The README's "Wrap it in an app" section shows the same six lines for app authors:

import path from 'node:path'

const addon = path.join(path.dirname(process.execPath), '..', 'Frameworks', 'gpuix-native.darwin-arm64.node')
process.env.NAPI_RS_NATIVE_LIBRARY_PATH ??= addon

await import('./chat.tsx')

NAPI_RS_NATIVE_LIBRARY_PATH is the first path the generated packages/native/index.js loader checks. --external '*.node' stops Bun from embedding the addon at bundle time; without it the addon is embedded and extracted whatever the variable says. The app is resealed with codesign --force --deep --sign - after the addon is in place.

	main	This PR
.app executable	91 MB (addon embedded)	62 MB
.bun-*.node written to $TMPDIR on launch	yes	no

The app opens through open -W -n and renders. Notarisation is not tested: there is no Developer ID certificate available. The README's cargo-packager variant copies and signs the addon after cargo packager runs; that sequence was not run end to end because cargo-packager is not installed here.

Risk: apps that follow the old README keep working, still embedding the addon. Reverting the commit restores the embedded layout.

🤖 Generated with Claude Code