Add README.md and RUNBOOK.md per engineering standards

Create the two required documentation files for MCNS:
- README.md: project overview, quick-start (build/configure/run), links
  to ARCHITECTURE.md and RUNBOOK.md
- RUNBOOK.md: operator-focused procedures with numbered steps covering
  health checks, start/stop/restart, backup/restore, log inspection,
  and incident playbooks for database corruption, certificate expiry,
  MCIAS outage, DNS resolution failures, and port conflicts

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

README.md

@@ -0,0 +1,42 @@
+# MCNS
+
+Metacircular Networking Service -- an authoritative DNS server for the
+Metacircular platform. MCNS serves DNS zones backed by SQLite, forwards
+non-authoritative queries to upstream resolvers, and exposes a gRPC and
+REST management API authenticated through MCIAS. Records are updated
+dynamically via the API and visible to DNS immediately on commit.
+
+## Quick Start
+
+Build the binary:
+
+```bash
+make mcns
+```
+
+Copy and edit the example configuration:
+
+```bash
+cp deploy/examples/mcns.toml /srv/mcns/mcns.toml
+# Edit TLS paths, database path, MCIAS URL, upstream resolvers
+```
+
+Run the server:
+
+```bash
+./mcns server --config /srv/mcns/mcns.toml
+```
+
+The server starts three listeners:
+
+| Port | Protocol | Purpose |
+|------|----------|---------|
+| 53 | UDP + TCP | DNS (no auth) |
+| 8443 | TCP | REST management API (TLS, MCIAS auth) |
+| 9443 | TCP | gRPC management API (TLS, MCIAS auth) |
+
+## Documentation
+
+- [ARCHITECTURE.md](ARCHITECTURE.md) -- full technical specification, database schema, API surface, and security model.
+- [RUNBOOK.md](RUNBOOK.md) -- operational procedures and incident response for operators.
+- [CLAUDE.md](CLAUDE.md) -- context for AI-assisted development.