fix(init): use prek when installing hooks if pre-commit is missing

[DSeaStar]

Description

cz init already treated prek as a valid hook installer (is_pre_commit_installed()), but the install step always ran pre-commit install. When only prek is on PATH, that raises FileNotFoundError.

This change:

• Lists available installers (pre-commit, prek)
• Uses the only one present
• Asks which to use when both are installed
• Invokes <installer> install --hook-type ...

Fixes #2018

Checklist

• I have read the contributing guidelines

Was generative AI tooling used to co-author this PR?

• Yes (please specify the tool below)

Generated-by: Cursor Grok following the guidelines

Code Changes

• Add test cases to all the changes you introduce
• Run uv run poe all locally to ensure this change passes linter check and tests
• Manually test the changes:
  • Verify the feature/bug fix works as expected in real-world scenarios
  • Test edge cases and error conditions
  • Ensure backward compatibility is maintained
  • Document any manual testing steps performed
• Update the documentation for the changes

Manual testing: unit tests cover only-prek, only-pre-commit, both (prompt), and neither (InitFailedError). ruff check and mypy pass on the touched files. I did not run the full interactive cz init UI in a throwaway repo.

Documentation Changes

• Run uv run poe doc locally to ensure the documentation pages renders correctly
• Check and fix any broken links (internal or external)

Docs change is a one-line note in docs/commands/init.md. I did not rebuild the full mkdocs site.

Expected Behavior

• Only prek installed: cz init runs prek install
• Only pre-commit installed: same as today (pre-commit install)
• Both installed: prompt, then run the chosen installer
• Neither installed: InitFailedError mentioning both tools

Steps to Test This Pull Request

1. Install commitizen and prek only (no pre-commit on PATH)
2. Run cz init and select a hook type
3. Confirm hooks are installed via prek and no FileNotFoundError
4. Repeat with only pre-commit, then with both (should prompt)

Additional Context

Owner-confirmed in #2018 (issue-status: wait-for-implementation). Desired behavior is from the issue: treat the two tools as interchangeable, auto-select when only one is present, ask when both are.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.25%. Comparing base (93c7b51) to head (bb343bc).
⚠️ Report is 6 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2065   +/-   ##
=======================================
  Coverage   98.24%   98.25%           
=======================================
  Files          61       61           
  Lines        2799     2815   +16     
=======================================
+ Hits         2750     2766   +16     
  Misses         49       49           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

[woile]

Thanks for the PR, one comment only

[woile]

What if the user doesn't have any installed and doesn't want to use any of these? Like myself.

Maybe if nothing is installed, it should prompt:

No pre-commit hook detected, skipping question

so users who want this know how to act accordingly (install pre-commit and retry).

What do you think?

[DSeaStar]

Agreed — if neither pre-commit nor prek is installed we skip the question now and print that message.

[DSeaStar]

Addressed in c9ea08e: when neither pre-commit nor prek is on PATH, cz init now skips the hook question entirely and prints No pre-commit hook detected, skipping question, so users who want hooks know to install one and re-run.

I also noticed codecov flagged one uncovered line — the InitFailedError branch in _ask_hook_installer(). I kept it as a guard against the installer disappearing between the question and the install step (e.g. PATH change), and added a test for it in bb343bc instead of removing it.

Could you take another look when you get a chance? Thanks!