chore: extract arcade into standalone repo

Arcade lives as its own pnpm workspace at ~/Documents/Code/arcade
now, with no @mana/* coupling. This drops every reference and the
games/ directory from the monorepo.

Removes:
- games/ directory (89 files: web + server + 22 HTML games + screenshots)
- @arcade/web, @arcade/server pnpm workspace entries (games/* globs)
- arcade scripts in root package.json (4 scripts)
- arcade.mana.how from mana-auth trusted origins + CORS_ORIGINS
- arcade entries in mana-apps registry, app-icons, URL overrides
- arcade.mana.how from cloudflared tunnel + prometheus blackbox probes
- arcade-web service block in docker-compose.macmini.yml
- generate-env.mjs entries for arcade server + web
- BRANDING_ONLY 'arcade' entry in registry consistency spec
- dead arcade translation keys in GuestWelcomeModal (DE+EN)
- arcade mention in CLAUDE.md, authentication guideline, MODULE_REGISTRY

Verified:
- services/mana-auth/src/auth/sso-config.spec.ts: 8/8 pass
- pnpm install regenerates lockfile cleanly (-536 lines)
- no remaining 'arcade' refs outside historical snapshot docs

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

CLAUDE.md

@@ -25,7 +25,6 @@ apps/
 ├── memoro/apps/     # Only remaining mobile app (Expo SDK 55)
 ├── {product}/       # Per-product landing pages, packages
 │                    # Standalone (own container, not unified): manavoxel
-games/               # arcade, voxelava, whopixels, worldream
 services/            # Backend services (Hono/Bun, Go, Python) — see list below
 packages/            # Shared workspace packages (@mana/*)
 docs/                # Long-form docs (deployment, hardware, postmortems, etc.)
@@ -165,7 +164,7 @@ Enforced by `pnpm run validate:turbo` (`scripts/validate-no-recursive-turbo.mjs`
 | `@mana/shared-theme` | Theme config |
 | `@mana/shared-i18n` | i18n |
 | `@mana/shared-privacy` | Unified visibility/privacy system: `VisibilityLevel` enum + zod schema + `<VisibilityPicker>` + predicates (`canEmbedOnWebsite`, …). Plan: [`docs/plans/visibility-system.md`](docs/plans/visibility-system.md). Rollout per-module, not yet adopted anywhere. |
-| `@mana/local-store` | Local-first store primitives — used by unified Mana, manavoxel, arcade, and shared-uload/-stores/-links |
+| `@mana/local-store` | Local-first store primitives — used by unified Mana, manavoxel, and shared-uload/-stores/-links |
 | `@mana/local-llm` | Browser-local LLM inference (transformers.js + Gemma 4 E2B, WebGPU). Powers `/llm-test` and the playground module. See [`packages/local-llm/CLAUDE.md`](packages/local-llm/CLAUDE.md) for the CSP requirements and the transformers.js v4 gotchas. |
 | `@mana/local-stt` | Browser-local speech-to-text (transformers.js + Whisper, WebGPU). Powers the QuickInputBar mic button. Same architecture as local-llm. See [`packages/local-stt/CLAUDE.md`](packages/local-stt/CLAUDE.md). |