fix(ci): use absolute path for lua-language-server --configpath

Problem: --configpath is resolved relative to the workspace root passed
to --check (lua/), not CWD. So .luarc.json was looked up at lua/.luarc.json
and not found, leaving vim and jit as undefined globals.

Solution: expand to an absolute path with $(pwd) at shell invocation
time, matching what the GitHub CI action already does.

scripts/ci.sh

@@ -6,5 +6,5 @@ git ls-files '*.lua' | xargs nix develop --command selene --display-style quiet
 nix develop --command prettier --check .
 nix fmt
 git diff --exit-code -- '*.nix'
-nix develop --command lua-language-server --check lua/ --configpath .luarc.json --checklevel=Warning
+nix develop --command lua-language-server --check lua/ --configpath "$(pwd)/.luarc.json" --checklevel=Warning
 nix develop --command busted