chore: add changeset for v3.21.5 patch release

[mrubens]

Important

Patch release v3.21.5 fixes QdrantClient URL handling, improves LM Studio model detection, and resolves Claude Code JSON parsing issues.

• QdrantClient:
  • Fix URL prefix handling during initialization.
• LM Studio:
  • Improve model detection to display all downloaded models.
• Claude Code provider:
  • Resolve JSON parsing issues and improve reasoning block display.

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