fix(nodejs plugin): warn when Corepack is enabled but unavailable

[mikeland73]

Summary

Fixes #2791.

When DEVBOX_COREPACK_ENABLED is set, the nodejs plugin's init_hook runs corepack enable. Some Node packages no longer bundle Corepack — notably nodejs-slim (nixpkgs#487796) and Node.js 25+. In those cases the corepack binary is missing, the enable step failed silently, and the user later hit a cryptic error with no indication of the cause:

bash: corepack: command not found
bash: yarn: command not found

Fix

• plugins/nodejs/setup-corepack.mjs: detect the missing corepack binary (ENOENT) when running corepack enable and print an actionable warning pointing the user to add the corepack package, instead of failing silently. Package-manager activation is skipped when Corepack couldn't be enabled. Other failures (e.g. being offline) are still ignored so they never block shell initialization.

  [devbox] Warning: DEVBOX_COREPACK_ENABLED is set but the `corepack` command
  was not found. Some Node packages (such as nodejs-slim, and Node.js 25+) no
  longer bundle Corepack. Add the `corepack` package to your devbox.json (for
  example, run `devbox add corepack`) to use Yarn or pnpm.
  

• plugins/nodejs.json: bump the plugin version to 0.0.5 (so existing projects regenerate the script) and clarify the readme to call out nodejs-slim alongside Node.js 25+.

• testscripts/plugin/nodejs_corepack_autodetect.test.txt: add a case that switches the project to nodejs-slim and asserts the shell still initializes successfully and the warning is printed.

How was it tested?

• go test ./plugins/... passes.
• node --check on the script passes, and I exercised it directly under Node 22:
  • no-op when DEVBOX_COREPACK_ENABLED is unset;
  • with corepack on PATH: installs the yarn/pnpm/... shims into the bin dir, exit 0;
  • with corepack removed from PATH: prints the warning, exits 0, does not crash.
• Added testscript coverage for the nodejs-slim (no bundled Corepack) path.

cc @apgrucza (issue reporter)

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Generated by Claude Code

[Copilot]

Pull request overview

This PR updates the Node.js plugin’s Corepack setup to explicitly warn (instead of failing silently) when DEVBOX_COREPACK_ENABLED is set but the corepack binary is missing (notably with nodejs-slim and Node.js 25+), and adds test coverage for that scenario.

Changes:

• Add ENOENT detection around corepack enable and emit an actionable warning when Corepack is unavailable; skip package-manager activation in that case.
• Bump the nodejs plugin version and clarify the plugin readme about nodejs-slim / Node.js 25+ Corepack availability.
• Extend testscript coverage to assert shell initialization succeeds and the warning is printed when using nodejs-slim.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
testscripts/plugin/nodejs_corepack_autodetect.test.txt	Adds a nodejs-slim case to verify the Corepack-missing path warns and doesn’t break shell init.
plugins/nodejs/setup-corepack.mjs	Adds corepack-missing detection and warning; gates package-manager activation on successful Corepack enablement.
plugins/nodejs.json	Bumps plugin version and updates readme to mention nodejs-slim and Node.js 25+ Corepack behavior.

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