feat(flags): declare bus-auth and bus-tls feature flags (off)

bus-auth carries the off -> soft -> enforce rollout state; bus-tls is a
boolean. Both start disabled so master keeps compiling and passing tests
while the auth/TLS code lands behind them across phases 0001a-0001e.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

dev/feature_flags.json

@@ -0,0 +1,19 @@
+{
+  "flags": {
+    "bus-auth": {
+      "enabled": false,
+      "state": "off",
+      "issue": "0001",
+      "description": "Signed control-plane auth + NATS nkey auth. Rollout: off -> soft (verify+log, allow) -> enforce (reject). 'enabled' mirrors state!=off.",
+      "added": "2026-06-07",
+      "enabled_at": null
+    },
+    "bus-tls": {
+      "enabled": false,
+      "issue": "0001",
+      "description": "TLS on the NATS data plane using the project's self-signed CA (deploy/tls/). When enabled the server presents its cert and clients pin the CA.",
+      "added": "2026-06-07",
+      "enabled_at": null
+    }
+  }
+}