chore(agent): drop .claude/skills — AGENTS.md carries the routing

The skill shims became redundant once the auto-loaded entry point
(CLAUDE.md → AGENTS.md) explicitly instructs reading VERIFICATION.md /
THEME-DESIGN.md; their only remaining value was explicit /nomarchy and
/theme invocation. The adapter is now permissions + subagent defs only.
References updated (AGENTS.md, agent/README.md, docs/README.md, README
tree, MEMORY.md hygiene note).

Verification: V0 (docs/meta only).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

AGENTS.md

@@ -18,7 +18,7 @@ thin *adapter* (see bottom) and never holds shared content.
 | **`docs/VISION.md`** | Product themes toward **v1.0** (not a queue) |
 | **`docs/ROADMAP.md`** | Design history + shipped log |
 | **`docs/README.md`** | Full documentation map |
-| **`.claude/`** | Claude Code adapter only (permissions, subagents, skill shims) — not the backlog |
+| **`.claude/`** | Claude Code adapter only (permissions, subagent defs) — not the backlog |
 
 ## If you're here to work autonomously (the loop)
 Follow **`agent/LOOP.md`** — one iteration: orient → pick one BACKLOG