Display password metavar value as TEXT, not STRING

[rolandwalker]

Description

Display password metavar value as TEXT, not STRING, to match other items in the helpdoc

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]

1. Low Missing regression test for CLI help metavar change
   File: mycli/main.py:146
   The PR changes only display text (STRING -> TEXT) for the --password option type, but there is no test asserting --help output for this option. Add a small CliRunner test that checks the --password help line includes TEXT so future refactors of the custom ParamType don’t silently revert behavior.

No correctness or security bugs were identified in this patch beyond that test coverage gap.