chore: enforce Node 24 for local dev (#345)

The vite-plugin build (`tsdown`) fails on Node < 24 with
`Failed to import module "unrun"`. tsdown 0.22.0 selects its config-file
loader at runtime: Node 24 exposes native TS stripping
(`process.features.typescript`), so it uses the "native" loader; on older
Node it falls back to "unrun", which tsdown does not declare as a
dependency. CI runs on Node 24 (engines.node: "24.x") so it passes there;
only local dev on Node 22 broke.

Align local dev with the already-declared/CI Node version rather than
working around it:

- Add .nvmrc (24) so `nvm use`/`nvm install` selects the right version.
- Set engineStrict: true in pnpm-workspace.yaml so `pnpm install` fails
  fast with a clear ERR_PNPM_UNSUPPORTED_ENGINE message instead of the
  cryptic downstream `unrun` error. (pnpm 11 reads config from
  pnpm-workspace.yaml in this repo, matching the existing camelCase keys.)
- Document the Node 24 prerequisite in README.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: interacsean

.nvmrc

@@ -0,0 +1 @@
+24

README.md

@@ -31,6 +31,16 @@ For users building applications with AppShell, see the detailed guides in `docs/
 
 This project is a monorepo managed with pnpm.
 
+### Prerequisites
+
+This project requires **Node.js 24** (see `engines` in `package.json`; CI runs on Node 24). Some build tooling (`tsdown`) relies on Node 24's native TypeScript config loading — on older versions it falls back to a loader that isn't installed, and the build fails. `engine-strict` is enabled, so `pnpm install` will refuse to run on an unsupported version.
+
+If you use [nvm](https://github.com/nvm-sh/nvm), a `.nvmrc` is provided:
+
+```bash
+nvm use      # or: nvm install
+```
+
 ### Setup
 
 ```bash

pnpm-workspace.yaml

@@ -79,3 +79,10 @@ trustPolicyExclude:
 
 # Save exact versions when adding dependencies
 saveExact: true
+
+# Enforce the Node version declared in package.json `engines` (24.x).
+# Without this, pnpm only warns on Node < 24 and the install proceeds,
+# leading to a cryptic build failure: tsdown's config loader needs Node 24's
+# native TypeScript stripping and otherwise falls back to `unrun` (not a
+# tsdown dependency). Fail fast at install time instead. See README "Development".
+engineStrict: true