Fix volcanic-agents user config: token → password

NATS's authorization.users entries don't accept a `token` field
(only `user+password`, `nkey`, or JWT). `token` at the top of the
authorization block is a single global token. NATS was crash-looping
with "unknown field 'token'" at line 20 col 32 of nats-server.conf.

Wire the NATS_VOLCANIC_AGENTS_TOKEN env var through the password
field instead. Env-var name stays the same — semantically the value
is still a bearer token, only the NATS field it's carried in changes.
CLAUDE.md and credentials.local.json updated accordingly.

docker-compose.yml

@@ -40,7 +40,7 @@ configs:
       authorization {
         users = [
           { user: "${NATS_USER}", password: "${NATS_PASSWORD}" },
-          { user: "volcanic-agents", token: "${NATS_VOLCANIC_AGENTS_TOKEN}" }
+          { user: "volcanic-agents", password: "${NATS_VOLCANIC_AGENTS_TOKEN}" }
         ]
       }