Problem: if no git credential helper is configured, login and
submit silently fail to persist credentials.
Solution: add `has_helper()` to `git_credential.lua` that checks
`git config credential.helper`. Guard the top of `login()`,
`logout()`, and `submit()` with an early-return error. Add a
healthcheck warning when no helper is configured. Add LuaCATS
annotations to all `git_credential` functions.
Problem: all healthcheck items were under a single `[required]`
section, including optional tools like uv and git.
Solution: move uv/nix/git checks into a new `[optional]` section.
Add git version check asserting >= 1.7.9 with the minimum and
installed versions shown side by side. Show neovim version the
same way.
## Problem
CodeChef had no working login, submit, or contest list. The browser
selectors were wrong, the contest list was missing present/past
contests,
and problem/contest URLs were unset.
## Solution
Fix login and submit selectors for the Drupal-based site. Paginate
`/api/list/contests/past` to collect all 228 Starters, then expand each
parent contest into individual division entries (e.g. `START228 (Div.
4)`).
Add language IDs, correct `url`/`contest_url`/`standings_url` in
metadata,
and make `:CP <platform>` open the contest picker directly.
Problem: vim.loop is deprecated since Neovim 0.10 in favour of vim.uv.
Five call sites across scraper.lua, setup.lua, utils.lua, and health.lua
still referenced the old alias.
Solution: replace every vim.loop reference with vim.uv directly.
