chore: consolidate the skill packages under .agents/

The repository had two skill directories. `skills/` held the four written
for this project; `.agents/skills/` held the ones the agent context refers
to. Nothing said which an agent should read, and `.agents/ORCHESTRATOR.md`
only ever pointed at the second.

Move the first four into `.agents/skills/` so there is one location, and
add the vendored packages this chapter work used: `animation-vocabulary`
and `improve-animations` (emilkowalski/skills), `teach` (mattpocock/skills),
plus a local `translation` skill and `audit-translations.mjs` for the EN/PT
pairs.

`skills-lock.json` pins the vendored three by source and content hash, so a
later re-vendor is a diff rather than a guess. `.claude/skills/` is
symlinks into `.agents/skills/`, which is what makes them loadable here
without a second copy on disk.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.agents/skills/rules-case-study/SKILL.md

@@ -0,0 +1,39 @@
+---
+name: rules-case-study
+description:
+  Use when explaining how a repository turns agent guidance into enforceable
+  behavior across context files, skills, CLI checks, Git hooks, CI, worktrees,
+  or PR review; build a concise, source-linked case-study page.
+---
+
+# Rules case study
+
+Show the control loop: context → skills → CLI → commit → review. The reader
+should see where a rule lives, what executes it, and how to verify it.
+
+## Workflow
+
+1. Inspect authoritative files before writing copy. Start with the repository
+   context file, skill directory, command or database ledger, enforcement
+   scripts, hooks, staged-file config, CI, and review policy. Use
+   [the interview source map](references/interview-source-map.md) as a routing
+   hint, then confirm paths in the target repository.
+2. Separate guidance from enforcement. A context file or skill teaches an agent;
+   a CLI check, hook, CI job, or reviewer blocks or reports behavior. Never
+   describe prose as mechanically enforced.
+3. For every example, show the rule, exact source path, enforcement point,
+   verification command, and remaining gap. Prefer one concrete ratchet or hook
+   example over a list of vague best practices.
+4. Add a skills shelf. Each skill needs a trigger, the lesson it carries, a tiny
+   example, and a source link. Keep examples short enough to copy into an agent
+   prompt.
+5. Include a read-only exploration prompt that asks an agent to map rules to
+   evidence and gaps. Add copy feedback and bilingual labels if the host guide
+   supports both languages.
+6. Use a dependency-free standalone page when the case study is mostly
+   explanatory. Link back to the main guide and exact source files. Do not
+   modify the source repository merely to document it.
+7. Verify dynamic stage and skill states, source links, copy behavior, language
+   switching, no horizontal overflow, and the 390px/1920px/3840px viewports. The
+   page is done when every claim has a source or is clearly labeled as a design
+   recommendation.