[Maintainer] Upgrade to v0.19.1

[github-actions]

[Maintainer] Upgrade to v0.19.1

Current version: 0.12.0
Target version: 0.19.1

Upgrade Notes

What's Changed

Other Changes

• chore: add v0.19.0 to releases.json by @ianlintner in chore: add v0.19.0 to releases.json caretaker#534
• fix(release): ensure caretaker:reviewed label exists before gh pr create by @ianlintner in fix(release): ensure caretaker:reviewed label exists before gh pr create caretaker#540
• feat: fleet-wide upgrade defaults — auto_approve + auto_ready_drafts (v0.19.1) by @ianlintner in feat: fleet-wide upgrade defaults — auto_approve + auto_ready_drafts (v0.19.1) caretaker#543

Full Changelog: ianlintner/caretaker@v0.19.0...v0.19.1

📋 Full Changelog

@copilot Please apply this upgrade.
See .github/agents/maintainer-upgrade.md for instructions.

FROM: 0.12.0
TO: 0.19.1
BREAKING: False

Steps:

1. Update version pins in pyproject.toml / requirements.txt
2. Update any workflow references
3. Run tests to verify compatibility
4. Update the version in config if applicable

Acceptance criteria:

• Version updated to target
• All tests pass
• No regressions