fzf search: ensure fullscreen with preview on

[rolandwalker]

Description

fzf search: ensure fullscreen with preview on, overriding environment variable FZF_DEFAULT_OPTS in part.

The mycli documentation describes the fzf search as fullscreen with a preview; these options selectively override parts of FZF_DEFAULT_OPTS from the environment to make sure that is always true.

The user's fzf keybindings, colors, and most other options are still taken from FZF_DEFAULT_OPTS if present.

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. Potential compatibility regression if fzf version doesn’t recognize --no-height or --preview-window ...:nohidden. This will cause the search to fail with “unknown option” on older fzf builds. Consider checking fzf --version or probing fzf --help once and conditionally including these flags, or provide a fallback that omits them. File: mycli/packages/toolkit/fzf.py:51

Missing tests / edge cases

1. No test coverage for option construction. A small unit test around search_history’s fzf_opts could assert that --no-height and --preview-window=down:wrap:nohidden are included, and that existing options remain unchanged. File: mycli/packages/toolkit/fzf.py:48

If you want, I can draft a minimal test that validates the options list without invoking fzf.