wiki(claude): add design-context pointers for admin-infra-project

Replaces seeded stub in Domain conventions with a 3-source pointer block:
1. concepts/admin-infra-project.md (canonical local design)
2. ~/projects/.workshop/.archive/2026-05-21-admin-infra-project.md (rationale)
3. .wiki/overview.md (orientation only)

Closes task admin-infra-project-pointers — bootstrap pointer for the
entire migration / agenda chain.

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

.wiki/CLAUDE.md

@@ -13,4 +13,12 @@ Curated knowledge base. Structure:
 
 ## Domain conventions
 
-(seeded by `[admin-infra-project-pointers]` task — see `.tasks/STATUS.md`)
+### Mandatory: read design context before implementation
+
+Before picking up any task in `.tasks/`, load the full design context. It does **not** live in this repo as a standalone source — only pointers do. Sources, in order:
+
+1. **Local design (canonical):** `.wiki/concepts/admin-infra-project.md` — ingested via promote 2026-05-21. Identity, scope, content inventory, migration recipe (subtree-split + read-tree merge for populated prefixes), initial agenda.
+2. **Brainstorm process trace (rationale):** `~/projects/.workshop/.archive/2026-05-21-admin-infra-project.md`. Why each decision was made (recommend vs menu trade-offs), what was rejected (filter-repo vs subtree-split, "admin-only" skills, splitting roadmap from ops), anti-patterns flagged during brainstorm.
+3. **Local `overview.md`** — thin summary, quick orientation only — never the source of truth.
+
+Do **not** invent migration recipes, file lists, taxonomies, or scope decisions from task `where_stopped` lines alone — those are pointers, not specifications. The concept doc and archive contain the rationale.