refactor(wiki): migrate this repo's .wiki/ to canonical Karpathy layout

Stop being inconsistent with our own fixed project-bootstrap template.

- SUMMARY.md → index.md (catalog by type, with one-line hooks)
- source/*.md → concepts/*.md (with `git mv` so history is preserved)
- WORKFLOW.md removed (workflow lives in wiki-maintainer, not duplicated here)
- New: .wiki/CLAUDE.md (project schema, Karpathy gist URL pinned at top)
- New: log.md (append-only op log; backfilled with prior decisions)
- New: overview.md (single project intro page)
- New: raw/README.md (immutability note; replaces .gitkeep placeholder)
- Empty .gitkeep added to entities/, packages/, sources/
- Migrated pages got `type: concept` frontmatter

After this, wiki-maintainer reads .wiki/CLAUDE.md → index.md as it expects,
and the layout matches what newly-bootstrapped projects will look like.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.wiki/overview.md

@@ -0,0 +1,29 @@
+---
+title: claude-skills overview
+type: overview
+updated: 2026-04-28
+---
+
+# claude-skills — overview
+
+Joint workshop where Vitya and Claude develop, test, and store Claude skills. Both editable sources (`skills/<name>/`) and built archives (`dist/<name>.skill`) live here, so a fresh machine can clone the repo and install every personal skill in one command.
+
+## Components
+
+- **`skills/`** — editable skill sources, one folder per skill (each with `SKILL.md` + optional `assets/`).
+- **`dist/`** — built `.skill` archives, committed so installs don't need a build toolchain on the target.
+- **`scripts/`** — `build.sh` / `build.ps1` (zip sources → archive), `install.sh` (copy sources → `~/.claude/skills/`).
+- **`.wiki/`** — Karpathy LLM Wiki for design decisions and gotchas. See [CLAUDE.md](CLAUDE.md) for schema.
+- **`.tasks/`** — task board (`STATUS.md`).
+- **`CLAUDE.md`** — repo-level agent instructions (skill triggers).
+
+## Where to look
+
+- New here? → [concepts/repo-layout.md](concepts/repo-layout.md), then `README.md`.
+- Working on a skill? → edit `skills/<name>/`, then `bash scripts/install.sh <name>` (or `pwsh scripts/build.ps1 <name>` to refresh the archive).
+- Tracking work? → [.tasks/STATUS.md](../.tasks/STATUS.md).
+- Made a non-trivial decision? → add a `concepts/<topic>.md` page, link from [index.md](index.md), append a line to [log.md](log.md).
+
+## Cross-references
+
+This page intentionally stays short. The substantive material lives in `concepts/` (decisions, gotchas) and the [index](index.md) catalog.