Describe one repo for contribution and simulation

Andrew Dunnrequested to merge
docs/one-repo into main

What

The README, the plugin and marketplace descriptions, AGENTS.md, SECURITY.md and CONTRIBUTING.md describe one repository that holds both contribution and simulation, with the 19 vendored skills listed and the SKILL_HOMES install documented. docs/relationship.svg, which drew two repositories, is removed.

Why

The contribution workflow and the vendored GitLab AI skills now live in this repository. The docs still called it "the environment half of a two-repository split", linked a sibling for install, and drew the split in a diagram, so a reader following the README would install a second plugin that this one replaces. SECURITY.md did not say where to report a flaw in vendored content.

How

  • README.md: the introduction names the three parts (simulation, contribution, vendored skills). Install carries the plugin lines, the SKILL_HOMES alternative from the contribution README (point the list at skills/ and vendor/gitlab-ai-skills/skills/), and the 19 vendored skills grouped by job, from vendor/gitlab-ai-skills/manifest.yml. The sibling paragraphs and the diagram reference go.
  • .claude-plugin/plugin.json, .claude-plugin/marketplace.json: the descriptions cover both jobs. The SKILL.md description is untouched, so the fire battery does not re-run.
  • docs/relationship.svg: removed. Only the README referenced it, and every panel depicted a second repository, so no windowed text edit made it accurate.
  • SECURITY.md: vendored content, unmodified from gitlab-org/ai/skills, is reported upstream. The vendoring machinery, the two patches and the authored skill are reported here.
  • CONTRIBUTING.md: the commit-trailers path points at skills/gitlab-simulation/scripts/lint-message.sh, and the patch paragraph names the caproni base of this skill instead of a sibling.
  • AGENTS.md: "What this is" and the repo shape name the vendored set.
  • CHANGELOG.md: one [Unreleased] entry under Changed.

Boundaries

  • No SKILL.md body or description changes, so neither the fire battery nor the fidelity test re-runs.
  • ADRs, sims/fire-battery.md, sims/fidelity-test.md and the released CHANGELOG sections keep their historical mentions of the old repository.
  • just ci passes, including vale-check in parity mode, word-budget (51848 of 52000) and commit-trailers.

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