fix(docs): update Discord invite link

[gkorland]

Summary

Replace the deprecated Discord invite link with the new one across all documentation files.

Changes

• Old link: https://discord.gg/ErBEqN9E
• New link: https://discord.gg/6M4QwDXn2w

Testing

N/A — documentation-only change.

Memory / Performance Impact

N/A

Related Issues

N/A

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: a1dcaaf1-b9ff-4f73-b65e-4ed196a5bb22

📥 Commits

Reviewing files that changed from the base of the PR and between 83d98fe and d430689.

📒 Files selected for processing (1)

• README.md

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/discord-link

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.53%. Comparing base (83d98fe) to head (d430689).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #32   +/-   ##
=======================================
  Coverage   86.53%   86.53%           
=======================================
  Files           1        1           
  Lines          52       52           
=======================================
  Hits           45       45           
  Misses          7        7           

Flag	Coverage Δ
unittests	86.53% <ø> (ø)

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