Composable asset pipeline with bun and TypeScript support

[jimsynz]

Summary

• Refactors phx.install.assets from a monolithic task into a composable orchestrator with pluggable bundler and CSS runner subtasks
• Adds Bun as an alternative bundler to esbuild, using the bun hex package — npm workspace deps instead of vendored JS, bun profiles for JS and CSS
• Adds --lang=ts option for both bundlers, generating a well-factored TypeScript entry point
• Tailwind CSS runner is dynamically dispatched via task naming convention (phx.install.assets.tailwind.#{bundler}), so adding a new bundler requires no changes to existing files

New flags on phx.install.assets

Flag	Values	Default
--bundler	esbuild, bun	esbuild
--lang	js, ts	js
--tailwind	boolean	true
--js-test	boolean	false

Task composition

phx.install.assets (orchestrator)
├── phx.install.assets.static
├── phx.install.assets.live_reload
├── phx.install.assets.esbuild OR phx.install.assets.bun
└── phx.install.assets.tailwind
    ├── phx.install.assets.tailwind.esbuild
    └── phx.install.assets.tailwind.bun

Test plan

• All 164 existing tests pass (0 failures)
• New tests cover: esbuild default, --no-tailwind, --lang ts, --bundler bun, --bundler bun --lang ts, --js-test opt-in and default-off
• Manual testing with mix phx.install.assets --bundler bun --lang ts in a fresh project
• Verify bun watcher and CSS profile work in dev

[LostKobrakai]

npm workspace deps

I'm not 100% sure, but I used file:{path} dependencies with phoenix_vite and it made bun fetch and use devDependencies of the packages under ../deps - which is generally not what you want. I only notices it because I installed playwright for phoenix_test and it never used the latest version I needed. Turns out live_view uses playwright as a dev dependency and I always got their version.

[LostKobrakai]

See LostKobrakai/phoenix_vite#21 for small amouts of context :D

[jimsynz]

Superseded — composable architecture extracted without bun support into a separate PR.