feat: Phase 0 workspace, spikes, and golden harness

Stand up the monorepo skeleton and land the first Phase 0 artifacts:
pairing threat model, plugin catalog, builder detect, 20-prompt golden
harness, and synthetic 2GB mirror timing.

.env.example

@@ -0,0 +1,18 @@
+# Copy to .env. Never commit real values.
+
+# API
+PORT=3000
+DATABASE_URL=postgres://wursor:wursor@localhost:5432/wursor
+REDIS_URL=redis://localhost:6379
+
+# Auth
+SESSION_SECRET=replace-me
+
+# LLM — Grok is the default adapter. Switch provider with LLM_PROVIDER.
+LLM_PROVIDER=grok
+XAI_API_KEY=
+LLM_FALLBACK_PROVIDER=
+
+# Sandbox
+DOCKER_HOST=
+WARM_POOL_HOT_SPARES=2