Fix npm bundle dump PATH

[MikeMcQuaid]

• Ensure npm list runs with npm's directory on PATH.
• This lets /usr/bin/env node resolve Homebrew's node.
• Add a regression for absolute npm shims.

Fixes #22331

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[Copilot]

Pull request overview

This pull request fixes brew bundle dump for npm packages by ensuring npm list is executed with the npm executable’s directory prepended to PATH, allowing /usr/bin/env node to resolve Homebrew’s node when npm is invoked via an absolute shim.

Changes:

• Wrap the npm list -g --json invocation in with_env(package_manager_env(npm)) so PATH includes the npm directory.
• Add an RSpec regression test asserting npm’s directory is placed at the front of PATH during package listing.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
Library/Homebrew/bundle/extensions/npm.rb	Ensures npm list runs under a PATH that includes the npm executable’s directory.
Library/Homebrew/test/bundle/npm_spec.rb	Adds a regression test validating PATH behavior for absolute npm shims during dumping.

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