Remove empty admin UI stubs

The internal/admin/ package was never imported or mounted — just
placeholder files. Removing to avoid confusion before the real
dashboard is built.

CLAUDE.md

@@ -68,7 +68,7 @@ Startup (`cmd/control-plane/main.go`) wires: config (env vars) → pgxpool → `
 
 - **API Server** (`internal/api/server.go`): chi router with middleware. Creates handler structs (`sandboxHandler`, `execHandler`, `filesHandler`, etc.) injected with `db.Queries` and the host agent Connect RPC client. Routes under `/v1/sandboxes/*`.
 - **Reconciler** (`internal/api/reconciler.go`): background goroutine (every 30s) that compares DB records against `agent.ListSandboxes()` RPC. Marks orphaned DB entries as "stopped".
-- **Admin UI** at `/admin/` (htmx + Go html/template, no SPA, no build step)
+- **Admin UI** at `/admin/` (htmx + basecoat + alpine.js + Go html/template, no SPA, no build step)
 - **Database**: PostgreSQL via pgx/v5. Queries generated by sqlc from `db/queries/sandboxes.sql`. Migrations in `db/migrations/` (goose, plain SQL).
 - **Config** (`internal/config/config.go`): purely environment variables (`DATABASE_URL`, `CP_LISTEN_ADDR`, `CP_HOST_AGENT_ADDR`), no YAML/file config.
 

internal/admin/handlers.go

@@ -1 +0,0 @@
-package admin