Add slugified and subdomains to Vale vocabulary

[mintlify]

Summary

• Added slugified and subdomains? to the Vale vocabulary accept list
• These terms appear in files changed by PR Update AI feature docs and fix assistant API links #4630 and would be flagged by Vale.Spelling

---

Note

Low Risk
Low risk: only updates Vale spelling allowlist terms and does not affect runtime code or behavior.

Overview
Updates the Vale Mintlify accepted-vocabulary list to include slugified and subdomains?, preventing Vale.Spelling from flagging these terms in documentation.

^{Written by Cursor Bugbot for commit bce530c. This will update automatically on new commits. Configure here.}