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/teach/LEARNING-RECORD-FORMAT.md

@@ -0,0 +1,69 @@
+# Learning Record Format
+
+Learning records live in `./learning-records/` and use sequential numbering:
+`0001-slug.md`, `0002-slug.md`, etc. Create the directory lazily: only when the
+first record is written.
+
+They are the teaching equivalent of ADRs: they capture non-obvious lessons, key
+insights, and stated prior knowledge that will steer future sessions. They are
+used to calculate the zone of proximal development.
+
+## Template
+
+```md
+# {Short title of what was learned or established}
+
+{1-3 sentences: what was learned (or what prior knowledge was established), and
+why it matters for future sessions.}
+```
+
+That is the whole format. A learning record can be a single paragraph. The value
+is recording _that_ this is now known and _why_ it changes what to teach next,
+not in filling out sections.
+
+## Optional sections
+
+Only include these when they add genuine value. Most records won't need them.
+
+- **Status** frontmatter (`active | superseded by LR-NNNN`): useful when an
+  earlier understanding turns out to be wrong and is replaced.
+- **Evidence**: how the user demonstrated the understanding (a question
+  answered, an exercise completed, prior experience cited). Useful when the
+  claim might be revisited.
+- **Implications**: what this unlocks or rules out for future sessions. Worth
+  recording when non-obvious.
+
+## Numbering
+
+Scan `./learning-records/` for the highest existing number and increment by one.
+
+## When to write a learning record
+
+Write one when any of these is true:
+
+1. **The user demonstrated genuine understanding of something non-trivial**: not
+   just exposure, but evidence they can use the concept correctly. This sets a
+   new floor for what to teach next.
+2. **The user disclosed prior knowledge**: "I already know X." Record it so
+   future sessions don't re-teach it. Also record the _depth_ claimed.
+3. **A misconception was corrected**: the user previously believed something
+   wrong and now sees why. These are high-value: they predict future stumbling
+   blocks for related topics.
+4. **The mission shifted in response to learning**: the user discovered they
+   cared about something different than they thought. Cross-link to
+   [[MISSION.md]] and update it.
+
+### What does _not_ qualify
+
+- Material that was merely covered. Coverage is not learning. Wait for evidence.
+- Anything already captured tersely in [[GLOSSARY.md]] as a term definition.
+  Don't duplicate.
+- Session-by-session activity logs. Learning records are not a journal: they are
+  decision-grade insights.
+
+## Supersession
+
+When a later record contradicts an earlier one (the user's understanding
+deepened or corrected), mark the old record `Status: superseded by LR-NNNN`
+rather than deleting it. The history of how understanding evolved is itself
+useful signal.