Add sprint-stats, close-milestone skills and scripts to ai_initiative_marketing
> Follow-up to [ai_initiative#3586381](https://git.drupalcode.org/project/ai_initiative/-/work_items/3586381) (migration of AI Marketing Initiative to ai_initiative_marketing).
## Summary
Port the sprint management skills and scripts from `project/ai_initiative` to `project/ai_initiative_marketing`, and remove the now-obsolete Marketing issue templates from ai_initiative.
Additionally (slight scope expansion), document the relationship between this repo's project-specific skills and [`project/ai_best_practices`](https://git.drupalcode.org/project/ai_best_practices) — the foundational, higher-level layer of universal Drupal AI guidance these skills build on.
## Changes
### ai_initiative_marketing (this repo)
- Add `skills/sprint-stats/SKILL.md` -- sprint report generation skill
- Add `skills/close-milestone/SKILL.md` -- sprint-change workflow skill
- Add `scripts/run-sprint-stats.sh` -- sprint report generation script
- Add `scripts/run-close-milestone.sh` -- end-of-sprint workflow script
- Add `.gitignore` for generated `reports/` directory
- All project IDs updated to 212236 (`project/ai_initiative_marketing`)
- Reference [`ai_best_practices`](https://git.drupalcode.org/project/ai_best_practices) in the README as the foundational skills layer, documenting the precedence/override model
### ai_initiative (sibling PR)
- Remove 5 Marketing issue templates (Blog Entry, Case Study, Generic, Video, Webinar) -- these already exist in ai_initiative_marketing
- Add Total/Average summary row to the Aggregate Statistics table in sprint-stats report
## AI Best Practices layering (scope expansion)
[`project/ai_best_practices`](https://git.drupalcode.org/project/ai_best_practices) provides universal, opinionated AI-assisted-development guidance that applies across all Drupal work (core, contrib, custom). It sits at a **higher level** than the skills in this repo:
- This repo's skills are **project-specific** (sprints, milestones, credit attribution, GitLab CLI for the Marketing Initiative) and **layer on top of** `ai_best_practices` rather than replacing it.
- By default an AI assistant should **defer to `ai_best_practices`** for general Drupal + AI conventions.
- A skill here **may deliberately override an `ai_best_practices` skill** in specific circumstances where the Initiative's workflow differs. When it does, the override must be **explicit** — naming the upstream skill and the reason — so it is intentional and reviewable.
## Acceptance Criteria
- [ ] Sprint-stats and close-milestone skills work against ai_initiative_marketing milestones
- [ ] Marketing issue templates removed from ai_initiative
- [ ] Sprint report Aggregate Statistics table includes a bold Total/Average row
- [ ] README references [`ai_best_practices`](https://git.drupalcode.org/project/ai_best_practices) as the foundational, higher-level AI-guidance layer these skills build on
- [ ] README documents the precedence model: defer to `ai_best_practices` by default; this repo's skills add Initiative-specific guidance on top
- [ ] README states that a skill here may override an `ai_best_practices` skill in specific circumstances, and that any such override must be explicit (name the upstream skill + reason)
*Drafted with the assistance of AI (Claude Code / Opus 4.8).*
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