chore(skills): rename all skills to domain-action convention

Adopts the whatsinagame naming pattern where the domain comes
first and the action second (e.g. pr-review, sprint-start,
audio-gen). Updated all cross-references in settings, agents,
docs, and inter-skill references.

12 renames: commit→git-commit, create-skill→skill-create,
gen-audio→audio-gen, gen-image→image-gen, plan-sprint→sprint-plan,
push-pr→pr-push, render-sprite→sprite-gen, review-pr→pr-review,
search-docs→docs-search, start-sprint→sprint-start,
start-workshop→workshop-start.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/DEVOPS.md

@@ -281,7 +281,7 @@ The sync runs automatically as part of `make setup` and via pre-commit hook. Mar
 
 ## Commit Conventions
 
-See the `/commit` skill (`.claude/skills/commit/`) for full details. Summary:
+See the `/git-commit` skill (`.claude/skills/git-commit/`) for full details. Summary:
 
 - Conventional commits: `type(scope): summary`
 - Types: `feat`, `fix`, `refactor`, `chore`, `docs`, `data`, `loc`