Add RUNBOOK.md and expand README.md

Create operational runbook covering health checks, start/stop/restart
(MCP and Docker Compose), backup/restore, garbage collection, and
incident procedures for database corruption, TLS expiry, MCIAS outage,
disk full, and push/pull failures. Includes MCP service definition
reference for the two-component deployment (mcr-api + mcr-web).

Rewrite README from 2-line stub to full project overview with
quick-start instructions, binary descriptions, port tables, and links
to ARCHITECTURE.md and RUNBOOK.md per engineering standards.

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

README.md

@@ -1,3 +1,59 @@
-MCR is the Metacircular Container Registry
+# MCR
 
-This is a container registry integrated with MCIAS.
+Metacircular Container Registry -- an OCI Distribution Spec-compliant
+container registry for the Metacircular platform. MCR stores and serves
+container images with authentication delegated to MCIAS and a local
+policy engine for fine-grained access control. Metadata is stored in
+SQLite; blobs are stored as content-addressed files on the filesystem.
+
+## Quick Start
+
+Build the binaries:
+
+```bash
+make all
+```
+
+This produces three binaries:
+
+| Binary | Purpose |
+|--------|---------|
+| `mcrsrv` | Registry server (OCI + admin REST + gRPC) |
+| `mcr-web` | Web UI (htmx, communicates with mcrsrv via gRPC) |
+| `mcrctl` | Admin CLI |
+
+Copy and edit the example configuration:
+
+```bash
+cp deploy/examples/mcr.toml /srv/mcr/mcr.toml
+# Edit TLS paths, database path, storage paths, MCIAS URL
+```
+
+Run the server:
+
+```bash
+./mcrsrv server --config /srv/mcr/mcr.toml
+```
+
+The server starts two listeners:
+
+| Port | Protocol | Purpose |
+|------|----------|---------|
+| 8443 | TCP | HTTPS -- OCI Distribution endpoints + admin REST API |
+| 9443 | TCP | gRPC admin API (TLS, MCIAS auth) |
+
+Run the web UI:
+
+```bash
+./mcr-web server --config /srv/mcr/mcr.toml
+```
+
+| Port | Protocol | Purpose |
+|------|----------|---------|
+| 8080 | TCP | HTTP -- web UI (repository browsing, policy management) |
+
+## Documentation
+
+- [ARCHITECTURE.md](ARCHITECTURE.md) -- full technical specification, OCI compliance details, database schema, policy engine, and security model.
+- [RUNBOOK.md](RUNBOOK.md) -- operational procedures, health checks, backup/restore, incident response, and MCP deployment.
+- [CLAUDE.md](CLAUDE.md) -- context for AI-assisted development.