Fix copilot-setup-steps workflow npm cache path

[Copilot]

The workflow was caching and installing npm dependencies from pkg/workflow/js/ which doesn't contain a package.json. JavaScript dependencies are in actions/setup/js/.

Changes

• Updated cache-dependency-path from pkg/workflow/js/package-lock.json to actions/setup/js/package-lock.json
• Updated npm install step to run at actions/setup/js directory instead of pkg/workflow/js

Aligns with the pattern used in .github/workflows/ci.yml.

Original prompt

Fix the copilot-setup-steps node js installation. https://github.com/githubnext/gh-aw/actions/runs/20756955042/job/59601516188

Run actions/setup-node@395ad3262231945c25e8478fd5baf05154b1d79f
Found in cache @ /opt/hostedtoolcache/node/24.12.0/x64
Environment details
  (node:2185) [DEP0040] DeprecationWarning: The `punycode` module is deprecated. Please use a userland alternative instead.
  (Use `node --trace-deprecation ...` to show where the warning was created)
  node: v24.12.0
  npm: 11.6.2
  yarn: 1.22.22
/opt/hostedtoolcache/node/24.12.0/x64/bin/npm config get cache
/home/runner/.npm
Error: Some specified paths were not resolved, unable to cache dependencies.

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[pelikhan]

@copilot keep but run at actions/setup/js/

[Copilot]

Restored the npm ci step to run at actions/setup/js/ (commit 8a145d4)