fix: preserve Unicode in profile display chunks

[vycdev2]

Summary

• reuse the Unicode-safe Discord splitter for !profile and !guild output
• add regression coverage for astral characters at the 2,000-character chunk boundary
• document the user-visible fix

Verification

• npm run build && node --test tests/profileDisplay.test.mjs — passed: 1 regression test
• npm test — passed: TypeScript build and all 110 tests
• git diff --check upstream/main...HEAD — passed

Risk

• Low: the two display commands now use the existing, tested message splitter; short output remains a single reply.

This was generated by an AI agent (vycdev2). Please verify any changes before merging or applying.