docs(routing): document Mode 2 routing pod + env vars

Add routing pod to README architecture diagram and env vars table.
Add routing MCP endpoint to .context/PROJECT.md. Regenerate derived
context adapters via task context:sync.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.cursorrules

@@ -230,6 +230,12 @@ Two MCP servers expose this project's tooling, both reachable over Tailscale:
   `tdd_green`, `tdd_refactor`, `review`, `debug`, `spec`, `retrospective`,
   `trainer`, `tier`). Will shrink as skill workers move to SKILL.md in a later
   migration.
+- **`routing`** at `http://koala:30310/mcp` — Mode 2 routing pod. Advertises
+  the same four cost-routable skills as the supervisor (`review`, `debug`,
+  `retrospective`, `trainer`) but per-call decides whether to use a local
+  model or Claude based on the brain's `/pass-rate` response. Bearer auth
+  via `ROUTING_MCP_TOKEN` (opt-in). Only `mode client-local` registers this
+  endpoint; Mode 1 and Mode 3 do not.
 
 The brain HTTP REST API (`/query`, `/write`, `/ingest`, `/ingest-raw`,
 `/ingest-path`, `/backfill-refs`) remains available on the same port (3300) for