Let interactive prompt changes respect dynamic format strings

[rolandwalker]

Description

The interactive prompt command was calling get_prompt() to set the prompt format. But get_prompt() computes the substituted values of any format strings.

Therefore the interactive prompt command was "burning in" any dynamically-computed values such as the date or the database name as a static value.

This is a bug, and it differs from the behavior of setting the prompt option in ~/.myclirc, which works correctly here.

The fix is to set the prompt format directly to the argument to change_prompt_format(), because the argument is a format string.

Checklist

• I added this contribution to the changelog.md file.
• I added my name to the AUTHORS file (or it's already there).
• To lint and format the code, I ran

  uv run ruff check && uv run ruff format && uv run mypy --install-types .

[github-actions]

Findings

1. Missing test coverage: there’s no test asserting that interactive prompt changes keep dynamic placeholders (e.g., \\D, \\d) and update on subsequent prompts. Consider adding a test that sets the prompt via the interactive command, then changes the database or advances time and verifies the prompt re-renders with fresh values. mycli/main.py:424

Notes

• No correctness or security regressions spotted in the code change itself.

Suggested next steps

1. Add a CLI/integration test for prompt command with dynamic format tokens.