Update CHANGELOG.md

[justinxu421]

Update CHANGELOG.md with version 0.5.8 release notes.

This release includes several user experience improvements and bug fixes:

• New /copy command: Enables copying request IDs or response text to clipboard for easier sharing and reference
• OAuth authentication for MCP servers: Adds secure authentication support for Model Context Protocol servers
• Interactive session picker: Improves --resume command UX by showing a picker when no session ID is specified
• Enhanced command discoverability: Adds fuzzy search for slash commands and improves help command formatting
• Performance improvements: Optimizes file picker with better fuzzy search algorithm for large codebases
• Reliability fixes: Improves tool permission system regex matching and removes extra blank lines from agent responses

---

🤖 This description was generated automatically. Please react with 👍 if it's helpful or 👎 if it needs improvement.

[github-actions]

Review completed. The changelog entries for version 0.5.8 are clear, well-organized, and appropriately detailed. No suggestions at this time.