chore(deps): update common-ci-tasks to v4.19

See merge request !765

When measure_performance:true, fetch-performance-testing-skill.sh now
reads the RUBY env var (set by copier from the ruby answer) and
removes references/ruby/ when the project is not Ruby. The Ruby refs
(rspec-benchmark and Ruby profilers) describe Ruby gems that don't
apply to Go, Terraform, Helm, Jsonnet, etc.

Also drop the upstream skill's evals/ directory on install. It's
maintainer test infrastructure (eval prompts for skill quality
testing), not runtime the agent needs; keeping it caused downstream
linters (pre-commit's pretty-format-json) to rewrite the vendored
upstream JSON file and break pipelines.

Depends on the partition merged upstream at gitlab-org/ai/skills!76.
The fetch URL stays on the skills repo's main branch — no version pin
in this MR.

Tests: extends tests/standard.sh with assertions that the skill
installs without references/ruby/ for the non-Ruby case, and adds
tests/ruby.sh asserting both references/tooling/ and references/ruby/
are present in a Ruby project.

Closes #4535

Vishal Patel authored Jun 25, 2026 and Vishal Patel committed Jun 25, 2026

Set IFS=$'\n\t' alongside set -euo pipefail to prevent word
splitting surprises on filenames containing spaces. Applied from
GitLabDuo review suggestion on !756.

feat: gate ruby-only performance skill references on ruby answer

See merge request !756