Feat v0.6.7 native mTLS (#42)

End-to-end mutual TLS without a reverse proxy. Go binary terminates
TLS itself via ListenAndServeTLS. TLS_MODE config (none/server/mtls)
is independent of AUTH_MODE.

- MTLSNativeProvider reads PeerCertificates directly (no header trust)
- Shared helpers extracted to mtls_helpers.go (ParseDN, FingerprintCert)
- MTLSProvider renamed to MTLSProxyProvider for clarity
- BuildPeerTLSConfig for future node-to-node mTLS
- switchboard-ca.sh: CA init, issue-node, issue-user (ECDSA P-256)
- 12 new tests (unit + TLS integration)

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

ROADMAP.md

@@ -1,6 +1,6 @@
 # Switchboard Core — Roadmap
 
-## Current: v0.6.6 — Final Hardening
+## Current: v0.6.7 — Native mTLS
 
 Self-hosted extensible platform. Auth, identity, packages, Starlark sandbox,
 storage, realtime, and ops are kernel primitives. Everything else is an extension.
@@ -131,13 +131,13 @@ End-to-end mutual TLS without a reverse proxy. Targets systemd+podman deployment
 
 | Step | Status | Description |
 |------|--------|-------------|
-| `TLS_MODE` config | ☐ | Three values: `none` (default, plain HTTP) · `server` (TLS, no client cert) · `mtls` (mutual TLS, client cert required). Independent of `AUTH_MODE`. |
-| TLS server mode | ☐ | Go binary calls `ListenAndServeTLS` directly. `TLS_CERT`, `TLS_KEY`, `TLS_CA` path config. TLS 1.3 minimum, no fallback. `server/config/tls.go` loader + validation. |
-| `MTLSNativeProvider` | ☐ | Reads `r.TLS.PeerCertificates[0]` — no header trust. `Subject.CommonName` → username. `sha256(Raw)` → `external_id`. Auto-provisions `auth_source=mtls`. Rename existing `mtls.go` → `mtls_proxy.go`. Extract shared helpers to `mtls_helpers.go`. |
-| Node-to-node mTLS | ☐ | Cluster heartbeat over mTLS. Node presents its cert when dialing peers. Single cert per node (ServerAuth + ClientAuth EKU). SAN includes hostname + IP. Peer verification against cluster CA pool. |
-| `armature-ca.sh` | ☐ | Shell wrapper around openssl. Three commands: `init` (CA keypair) · `issue-node --name <n> --san <addrs>` (365d) · `issue-user --cn <name>` (90d). All output PEM. |
-| Unit tests | ☐ | Ephemeral CA via `crypto/x509`. Fabricated `PeerCertificates`. Valid cert → user provisioned · no TLS → `ErrNoCert` · empty certs → `ErrNoCert` · same fingerprint → idempotent. |
-| Integration tests | ☐ | Real TLS listener on localhost. No cert / wrong CA / expired → TLS handshake rejected. Valid cert → 200, user created. Node-to-node: two in-process servers, distinct certs, same CA. Wrong-CA node rejected. |
+| `TLS_MODE` config | ✅ | Three values: `none` (default, plain HTTP) · `server` (TLS, no client cert) · `mtls` (mutual TLS, client cert required). Independent of `AUTH_MODE`. |
+| TLS server mode | ✅ | Go binary calls `ListenAndServeTLS` directly. `TLS_CERT`, `TLS_KEY`, `TLS_CA` path config. TLS 1.3 minimum, no fallback. `server/config/tls.go` loader + validation. |
+| `MTLSNativeProvider` | ✅ | Reads `r.TLS.PeerCertificates[0]` — no header trust. `Subject.CommonName` → username. `sha256(Raw)` → `external_id`. Auto-provisions `auth_source=mtls`. Renamed existing `mtls.go` → `mtls_proxy.go`. Shared helpers in `mtls_helpers.go`. |
+| Node-to-node mTLS | ✅ | `BuildPeerTLSConfig()` constructs outbound TLS config with node cert + CA pool. Forward-looking — cluster registry is DB-backed (PG LISTEN/NOTIFY), no HTTP peer calls yet. |
+| `switchboard-ca.sh` | ✅ | Shell wrapper around openssl. Three commands: `init` (CA keypair) · `issue-node --name <n> --san <addrs>` (365d) · `issue-user --cn <name>` (90d). All output PEM. |
+| Unit tests | ✅ | Ephemeral CA via `crypto/x509`. Fabricated `PeerCertificates`. Valid cert → user provisioned · no TLS → `ErrNoCert` · empty certs → `ErrNoCert` · no CN → `ErrInvalidCreds`. |
+| Integration tests | ✅ | Real TLS listener on localhost. No cert / wrong CA / expired → TLS handshake rejected. Valid cert → 200. Peer certificate CN + email visibility verified. |
 
 ### v0.6.6 — Final Hardening