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>

skills-lock.json

@@ -0,0 +1,23 @@
+{
+  "version": 1,
+  "skills": {
+    "animation-vocabulary": {
+      "source": "emilkowalski/skills",
+      "sourceType": "github",
+      "skillPath": "skills/animation-vocabulary/SKILL.md",
+      "computedHash": "39319fc9a33c15be08666b3685f58666f042ff36bb902b7814c0834a5ba99df4"
+    },
+    "improve-animations": {
+      "source": "emilkowalski/skills",
+      "sourceType": "github",
+      "skillPath": "skills/improve-animations/SKILL.md",
+      "computedHash": "eeb219a407e325b687af88db25771cc3018e3148245604112f5ac6990b6fd79c"
+    },
+    "teach": {
+      "source": "mattpocock/skills",
+      "sourceType": "github",
+      "skillPath": "skills/productivity/teach/SKILL.md",
+      "computedHash": "b8a69574c7a019bed84e84313dc8bf02e1d1bf925ba43057d433217c63863206"
+    }
+  }
+}