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/skill-reviewer/SKILL.md

@@ -0,0 +1,41 @@
+---
+name: skill-reviewer
+description:
+  Review an Agent Skill package and produce a kind, evidence-backed improvement
+  brief. Use when assessing a SKILL.md, its trigger, instructions, scripts,
+  references, safety, or evaluation readiness; do not rewrite the package unless
+  asked.
+---
+
+# Skill reviewer
+
+Review the submitted package before proposing changes. Preserve the author's
+intent: this is a constructive assessment, not a replacement of their domain
+expertise.
+
+## Review flow
+
+1. Read `SKILL.md` and list bundled files. Check frontmatter validity,
+   package-name alignment, and whether the description says both what the skill
+   does and when it applies.
+2. Identify the narrow job, the expected inputs, safe boundaries, a default
+   workflow, and observable output. Mark any claim you cannot verify as a
+   question, not a defect.
+3. Recommend only additions that change execution: a small RULES section for
+   real invariants, a script for repeated fragile work, a reference for
+   conditional detail, or eval cases for behavior that matters.
+4. Flag secrets, destructive actions, network calls, and unclear approval
+   boundaries prominently. Never copy credentials into review artifacts.
+5. Return a friendly brief with: what already works, highest-value improvements,
+   suggested package layout, and a small set of realistic test prompts.
+
+## Quality bar
+
+- Prefer precise activation language over broad phrases such as "use for code."
+- Keep the main instructions lean; send conditional or lengthy material to
+  `references/` and explain exactly when to read it.
+- Favor evidence and defaults over generic rules or tool menus.
+- Recommend scripts only when they remove repeated, error-prone mechanics;
+  document prerequisites and use relative paths.
+
+Read [the review rubric](references/review-rubric.md) when scoring a package.