feat: split wiki — using-wiki (policy) + setup-wiki (one-time)

Rename `wiki-maintainer` to `using-wiki` (rename via git mv preserves
file history). Strip greenfield/bootstrap content out of it; add a
Prerequisites section that delegates to the new `setup-wiki` skill when
`.wiki/` is missing or non-canonical.

New `setup-wiki` skill: 6-phase procedure (sanity → discovery → plan +
confirm → backup → create/migrate → verify → report). Two modes —
greenfield (no `.wiki/`) and migrate (existing non-canon, e.g. SUMMARY.md
+ source/). Confirmation gate before any write. Templates for each canon
file (`CLAUDE.md` schema, `index.md`, `log.md`, `overview.md`,
`raw/README.md`) baked in.

`project-bootstrap` Step 3 now delegates to `setup-wiki` instead of
holding inline templates that drift from canon.

After this commit, `~/.claude/skills/wiki-maintainer/` still exists as a
stale install — the user will rm it manually after commit (c) lands the
tasks split.

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

.tasks/STATUS.md

@@ -15,10 +15,12 @@ _Updated: 2026-04-28_
 - [x] Build + install affected skills (loop in build.sh handles 6-arg invocation cleanly)
 
 #### (b) Split wiki
-- [ ] Rename `skills/wiki-maintainer/` → `skills/using-wiki/`; update `name:` in frontmatter
-- [ ] New `skills/setup-wiki/` (canonical layout creation, gated, derived from current "Bootstrap empty wiki" section + Karpathy gist)
-- [ ] Prerequisites section in `using-wiki` → invokes `setup-wiki` if `.wiki/` is missing/non-canon
-- [ ] `project-bootstrap` Step 3 delegates to `setup-wiki`
+- [x] `git mv skills/wiki-maintainer/ skills/using-wiki/` (history preserved as rename)
+- [x] Updated `name:` to `using-wiki` and description to include `use project wiki` trigger; H1 + headline rewritten
+- [x] New `skills/setup-wiki/SKILL.md` — 6 phases (sanity → discovery → plan+confirm → backup → 4a greenfield / 4b migrate → verify → report), with full templates for each canon file
+- [x] `using-wiki` Prerequisites section delegates to `setup-wiki` when layout missing/non-canon
+- [x] `project-bootstrap` Step 3 now delegates to `setup-wiki`; inline templates kept as reference only
+- [x] Stale `dist/wiki-maintainer.skill` removed
 
 #### (c) Split tasks
 - [ ] Rename `skills/task-status-wiki/` → `skills/using-tasks/`; update `name:`