Add release notes for up v0.49.0

[adamwg]

Description

Type of change

• Bug fix (typo, broken link, incorrect info)
• Content update (new info, clarification, reorganization)
• New content (new page, section, or guide)

Checklist

• I ran make vale-file FILE=docs/path/to/file.md locally for files changed (or will fix Vale suggestions in review)
• Links work and point to the right places
  - [ ] If this adds new content, I tested the examples/instructions

Additional notes

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
docs	Ready	Preview, Comment	Jun 12, 2026 7:20pm

[Upbound-CLA]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}