Fix datetime node

[andres-javier-lopez]

Description

Fix datetime node returned time. Previous implementation was returning always the same date, this fixes the prompt to always return the current time.

Type of change

• Bugfix
• New feature
• Documentation update
• Refactor
• Chore

Checklist

Please run through the checklist and mark the items off before requesting review.

• Tests added/updated for changes in behavior
• Linter/formatter run (make format / make lint)
• Documentation updated (if applicable)
• CHANGELOG.md updated with a short entry describing the change (Required)

[Copilot]

Pull request overview

Fixes the datetime node so it returns a prompt containing the current date/time at execution time (instead of a static timestamp captured at initialization).

Changes:

• Refactors DateTimeNode to generate the date/time prompt dynamically on invocation.
• Updates unit tests to validate the refreshed prompt behavior.
• Adds a NEXT changelog entry for the fix.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
assistant_core/builder/datetime.py	Changes the datetime node implementation to compute the prompt at call time.
tests/unit/test_datetime_builder.py	Updates tests to check the node output content and adds a “refresh” test.
CHANGELOG.md	Documents the datetime node fix under NEXT.