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/references/review-rubric.md

@@ -0,0 +1,13 @@
+# Review rubric
+
+Assess six dimensions: discoverability, scope, procedure, safety, resources, and
+proof.
+
+For each finding, state the observed evidence, the practical consequence, and
+the smallest helpful change. Do not call missing files a problem unless the
+workflow genuinely needs them. A strong review explains why the recommendation
+belongs in the skill rather than in general agent behavior.
+
+Test prompts should include one normal request and one boundary case. Assertions
+should be observable, such as valid JSON, an explicit approval request before
+mutation, or a report containing file locations.