Initial CoreDNS setup as MCNS precursor

Serves two internal zones for the Metacircular platform:
- svc.mcp.metacircular.net (service addresses)
- mcp.metacircular.net (node addresses)

Forwards all other queries to 1.1.1.1 and 8.8.8.8. Includes rift
deployment compose with CoreDNS 1.12.1 and zone files mapping
metacrypt and rift to their LAN and Tailscale addresses.

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

CLAUDE.md

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+# CLAUDE.md
+
+## Overview
+
+MCNS precursor — a CoreDNS instance serving internal DNS zones for the
+Metacircular platform until the full MCNS service is built.
+
+## Zones
+
+| Zone | Purpose |
+|------|---------|
+| `svc.mcp.metacircular.net` | Internal service addresses (e.g. `metacrypt.svc.mcp.metacircular.net`) |
+| `mcp.metacircular.net` | Node addresses (e.g. `rift.mcp.metacircular.net`) |
+
+Everything else forwards to 1.1.1.1 and 8.8.8.8.
+
+## Files
+
+- `Corefile` — CoreDNS configuration
+- `zones/` — Zone files (manually maintained until MCP manages them)
+- `deploy/docker/docker-compose-rift.yml` — Docker compose for rift deployment
+
+## Operations
+
+```bash
+# Start
+docker compose -f deploy/docker/docker-compose-rift.yml up -d
+
+# Test resolution
+dig @192.168.88.181 metacrypt.svc.mcp.metacircular.net
+dig @192.168.88.181 rift.mcp.metacircular.net
+
+# After editing zone files, bump the serial and restart
+docker compose -f deploy/docker/docker-compose-rift.yml restart
+```
+
+## Adding a service
+
+1. Add an A record to `zones/svc.mcp.metacircular.net.zone`
+2. Bump the serial number (YYYYMMDDNN format)
+3. Restart CoreDNS
+
+## Adding a node
+
+1. Add an A record to `zones/mcp.metacircular.net.zone`
+2. Bump the serial number
+3. Restart CoreDNS