Set up prompt/continuation color configuration

[rolandwalker]

Description

The prompt and continuation color configurations were already available in the code, but examples of the relevant settings were not present in ~/.myclirc.

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. Changelog regression: duplicated release section

• File: changelog.md:1, changelog.md:9
• The PR adds a second 1.58.0 (2026/02/28) header instead of adding to the existing section. This can break changelog parsing/release-note tooling and fragments entries for the same release.
• Action: Move * Set up customization of prompt/continuation colors in ~/.myclirc. under the existing 1.58.0 → Features list and remove the duplicate header block.

Other checks

• No security issues found in the PR changes.
• No functional code-path changes; no additional runtime tests are strictly required for the myclirc example-key additions.