Add simple Add* recipes for GitLab CI/CD best practices

[scuba10steve]

Summary

• Adds four simple Add* recipes that wrap MergeYaml to set common defaults in .gitlab-ci.yml

• AddInterruptible — sets interruptible: true in default: or a named job

• AddTimeout — sets a timeout: duration

• AddArtifactsExpireIn — sets artifacts: expire_in: to prevent storage bloat

• AddDefaultKeyword — generic recipe to add any keyword/value under default:

• All support optional jobName and acceptTheirs parameters

• Includes full test coverage for each recipe

• Closes Add simple Add* recipes for GitLab CI/CD best practices #33

Test plan

• ./gradlew build passes (compiles, all tests green, CSV validation passes)
• recipes.csv contains only the 4 new recipes (plus pre-existing ones)
• Review each recipe's @DocumentExample test for correctness