Evaluate Turborepo for workspace task caching

[danieliser]

Context

PR #1220 removes Nx in favor of native pnpm -r orchestration for package scripts (build:tsc, build:types, lint, etc.).

That simplification is working, but we intentionally give up Nx task caching. Local benchmarks showed warm package rebuilds are noticeably slower without a cache:

Step	Nx (cached)	pnpm -r
build:tsc	~1s	~9s
build:types	~1s	~3s

Cold builds are roughly equivalent (~21–23s for build:tsc).

Proposal

Evaluate Turborepo as a lighter alternative to Nx that could restore:

• Task caching for unchanged packages
• Topological task execution (dependsOn)
• Optional remote cache for CI

…without reintroducing the full Nx toolchain we removed.

Scope to investigate

• turbo.json task definitions for build:tsc, build:types, lint, format, clean
• Local cache hit rates on day-to-day dev workflows
• CI integration (turbo run + optional remote cache)
• Compare install/tooling overhead vs current pnpm-only setup
• Confirm compatibility with existing postinstall / prepack lifecycle approach

Acceptance criteria

• Document recommendation: adopt Turborepo, defer, or stay pnpm-only
• If adopted: warm rebuild time should be materially closer to former Nx cache performance without breaking fresh pnpm install --frozen-lockfile

Related

• chore: replace Nx workspace scripts with pnpm recursive commands #1220 — Nx removal PR