README: infrastructure boundary and per-technology learning spine; commit architecture/runtime/schemas/style papers

runtime/stack.md

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+# Stack
+
+Runtime stack. Minimal dependencies.
+
+## Layers
+
+| Layer | Tech | Notes |
+|---|---|---|
+| Runtime | Python 3.13, asyncio, nats-py | same venv as nimmer-lib |
+| State | PostgreSQL (Phoebe), psycopg2, asyncpg later | bare SQL; no ORM |
+| Event bus | NATS VM 122, port 30000, JetStream | gates, actions, zone state |
+| Edge API | FastAPI HTTP + native WebSocket | clients |
+| Workflows | Python state machines, k8s pods | ephemeral probes |
+| Harness host | omp --mode rpc JSONL | host, not brain |
+
+## Two buses
+
+- Internal: NATS.
+- External: HTTP/WebSocket edge gateway.
+- Gateway translates; runtime never speaks HTTP; clients never touch NATS directly.
+
+## JetStream: replay, not truth
+
+- register change stream: durable; restart rebuilds materialized register copy.
+- cycle trail stream: retention-bounded; replay decision/cycle/escalation/spawn.
+- durable consumers per client tier; each replays from its own sequence.
+- retention limits are policy; truth is in Phoebe.
+
+## Dependency budget
+
+Allow: nats-py, psycopg2/asyncpg, fastapi, uvicorn, stdlib.
+Refuse: Kafka, Redis, RabbitMQ, ORM now, second broker.
+Every new dependency must state its `why` here.
+
+Version: 0.2 | Updated: 2026-11-04