checklist for 2025.08

[arkiuat]

Improvements:

• Make DateTime.(modified-)julian-date take timezone into account (#5886) [5a1f7013]
• Elaborate a bit on possible error reason [133f44c8]
• Change enum's raku method to return valid code (#5936) [5e8d7f65]
• Make DateTime a value type (#5933) [15a2a9b1]
• Make confused error message less confused [f5648294]