chore(deps): bump github.com/anthropics/anthropic-sdk-go (#579)

Bumps [github.com/anthropics/anthropic-sdk-go](https://github.com/anthropics/anthropic-sdk-go) from 1.18.1 to 1.19.0.
- [Release notes](https://github.com/anthropics/anthropic-sdk-go/releases)
- [Changelog](https://github.com/anthropics/anthropic-sdk-go/blob/main/CHANGELOG.md)
- [Commits](https://github.com/anthropics/anthropic-sdk-go/compare/v1.18.1...v1.19.0)

---
updated-dependencies:
- dependency-name: github.com/anthropics/anthropic-sdk-go
  dependency-version: 1.19.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

go.mod

@@ -5,7 +5,7 @@ go 1.24.0
 toolchain go1.24.2
 
 require (
-	github.com/anthropics/anthropic-sdk-go v1.18.1
+	github.com/anthropics/anthropic-sdk-go v1.19.0
 	github.com/charmbracelet/lipgloss v1.1.0
 	github.com/fatih/color v1.18.0
 	github.com/fsnotify/fsnotify v1.9.0