Refine several items in the helpdoc

[rolandwalker]

Description

• refer to the "server" rather than the "database" in contexts such as the host and port
• among many, only --port had the Honors <variable> text; remove it
• a UDS has a path but is not a true file
• shorten some entries
• spell out "certificate"
• change wording so that zsh descriptive completions make more sense, preferring to lead with "Whether to"
• make metavars more consistent, and more consistent with text
• ~/.myclirc is usually written with the tilde

Checklist

• I added this contribution to the changelog.md file.
• I added my name to the mycli/AUTHORS.txt 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 .