Add support for new Claude Haiku 4.5

[brianevanmiller]

Claude just released Haiku 4.5, their fastest and cheapest model in 2025. Let's see how this puppy runs within Zed!

Announcement: https://www.anthropic.com/news/claude-haiku-4-5
Model Page: https://www.anthropic.com/claude/haiku
System Card: https://assets.anthropic.com/m/99128ddd009bdcb/Claude-Haiku-4-5-System-Card.pdf
Documentation: https://docs.claude.com/en/docs/about-claude/models/overview#model-comparison-table

API Model Name: claude-haiku-4-5-20251001

According to their FAQs:

When should I use Haiku 4.5?
Haiku 4.5 scores 73.3% on SWE-bench Verified, making it one of the world’s best coding models. Haiku 4.5 excels at parallelized execution, sub-agents, and high-volume operations, while Sonnet 4.5 delivers frontier performance for complex coding agents and sophisticated reasoning.

Pricing Page: https://claude.com/pricing#api
Input: $1/MTok
Output: $5/MTok

Prompt Caching
Write: $1.25/MTok
Read: $0.10/MTok