[openclaw-bot-mary]

Summary

Rename the misleading password const to mqttPasswordAnyValue and improve its documentation.

Before:

// password is sent as the MQTT password. Webull documents that any value is
// accepted; the App Key is carried as the user name.
const password = "webullapi4go"

After:

// mqttPasswordAnyValue is the MQTT password. Webull accepts any non-empty
// value; the App Key is carried as the user name (cfg.AppKey). The literal
// string is an arbitrary placeholder and carries no authentication weight.
const mqttPasswordAnyValue = "webullapi4go"

Why

• password is a misleading name — it implies the value carries auth weight
• Webull accepts any non-empty MQTT password; the real auth is in the App Key
• Self-documenting name reduces contributor confusion

Gate

• go build ./... ✅
• go vet ./... ✅

Closes #22.