Enforce pnpm-only usage: Remove npm lock file and update documentation

[Copilot]

Repository uses pnpm exclusively but contained package-lock.json from npm and had inconsistent documentation referencing npm.

Changes

• Removed package-lock.json
• Updated .gitignore to block package-lock.json and yarn.lock from future commits
• Updated README.md installation instructions from npm install to pnpm add
• Updated .github/copilot-instructions.md to explicitly enforce pnpm-only usage with stricter guidelines

Only pnpm-lock.yaml remains as the lock file, and all documentation now consistently references pnpm as the sole package manager.

Original prompt

I only want to use pnpm in this repo, remove any other lock file

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[hckhanh]

@copilot Update instruction to make sure only pnpm is used

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (a8bffa5) to head (d7c26e8).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #60   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            6         6           
  Lines          245       245           
  Branches        82        82           
=========================================
  Hits           245       245           

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[Copilot]

Copilot wasn't able to review any files in this pull request.

[codspeed-hq]

CodSpeed Performance Report

Merging #60 will not alter performance

_{Comparing copilot/remove-other-lock-files-again (d7c26e8) with main (a8bffa5)}

Summary

✅ 64 untouched

[Copilot]

@copilot Update instruction to make sure only pnpm is used

Updated both README.md and copilot-instructions.md to enforce pnpm-only usage:

• Changed installation instructions from npm install to pnpm add
• Made package manager requirements more explicit in copilot-instructions.md

Commit: d7c26e8

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud